diff --git a/README.md b/README.md
index 2493de40..aba11db9 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,37 @@ $ node bin/bcoin-cli wallet primary --passphrase=node
 $ node bin/bcoin-cli mempool
 ```
 
+### Creating a blockchain and mempool
+
+``` js
+var bcoin = require('bcoin');
+bcoin.protocol.network.set('regtest');
+var chain = new bcoin.chain({ db: 'memory' });
+var mempool = new bcoin.mempool({ chain: chain, db: 'memory' });
+var miner = new bcoin.miner({ chain: chain, mempool: mempool });
+
+// Create a block "attempt"
+miner.createBlock(function(err, attempt) {
+  if (err)
+    throw err;
+
+  // Mine the block on the worker pool (use mine() for the master process)
+  attempt.mineAsync(function(err, block) {
+    if (err)
+      throw err;
+
+    // Add the block to the chain
+    chain.add(block, function(err) {
+      if (err)
+        throw err;
+
+      console.log('Added %s to the blockchain.', block.rhash);
+      console.log(block);
+    });
+  });
+});
+```
+
 ### TX creation
 
 TODO
diff --git a/lib/bcoin/block.js b/lib/bcoin/block.js
index 0a8e74bf..9e5ea0ee 100644
--- a/lib/bcoin/block.js
+++ b/lib/bcoin/block.js
@@ -276,8 +276,6 @@ Block.prototype.getReward = function getReward() {
   var reward = Block.reward(this.height);
   var i;
 
-  assert(this.height !== -1);
-
   for (i = 1; i < this.txs.length; i++)
     reward.iadd(this.txs[i].getFee());
 
diff --git a/lib/bcoin/miner.js b/lib/bcoin/miner.js
index f85fe4a9..5b6aa2fe 100644
--- a/lib/bcoin/miner.js
+++ b/lib/bcoin/miner.js
@@ -44,8 +44,6 @@ function Miner(options) {
   this.timeout = null;
 
   this.block = null;
-  this.iterations = 0;
-  this._begin = utils.now();
 
   this._init();
 }
@@ -68,13 +66,13 @@ Miner.prototype._init = function _init() {
     this.mempool.on('tx', function(tx) {
       if (!self.running)
         return;
-      self.addTX(tx);
+      self.attempt.addTX(tx);
     });
   } else if (this.pool) {
     this.pool.on('tx', function(tx) {
       if (!self.running)
         return;
-      self.addTX(tx);
+      self.attempt.addTX(tx);
     });
   }
 
@@ -122,41 +120,40 @@ Miner.prototype.start = function start() {
 
   this.running = true;
 
-  // Reset iterations
-  this.iterations = 0;
-
   // Create a new block and start hashing
-  this.createBlock(function(err, block) {
+  this.createBlock(function(err, attempt) {
     if (err)
       return self.emit('error', err);
 
-    self.block = block;
+    if (!self.running)
+      return;
 
-    if (!self.mempool)
-      return self.iterate();
+    self.attempt = attempt;
 
-    self.mempool.getSnapshot(function(err, hashes) {
-      if (err)
-        return self.emit('error', err);
+    attempt.on('status', function(status) {
+      self.emit('status', status);
+    });
 
-      utils.forEachSerial(hashes, function(hash, next) {
-        self.mempool.getTX(hash, function(err, tx) {
-          if (err)
-            return next(err);
+    attempt.mineAsync(function(err, block) {
+      if (err) {
+        self.emit('error', err);
+        return self.start();
+      }
 
-          self.mempool.fillAllCoins(tx, function(err) {
-            if (err)
-              return next(err);
+      // Add our block to the chain
+      self.chain.add(block, function(err) {
+        if (err) {
+          if (err.type === 'VerifyError')
+            utils.debug('%s could not be added to chain.', block.rhash);
+          self.emit('error', err);
+          return self.start();
+        }
 
-            self.addTX(tx);
-            next();
-          });
-        });
-      }, function(err) {
-        if (err)
-          return self.emit('error', err);
+        // Emit our newly found block
+        self.emit('block', block);
 
-        self.iterate();
+        // `tip` will now be emitted by chain
+        // and the whole process starts over.
       });
     });
   });
@@ -168,11 +165,185 @@ Miner.prototype.stop = function stop() {
 
   this.running = false;
 
-  clearTimeout(this.timeout);
-  this.timeout = null;
+  if (this.attempt) {
+    this.attempt.destroy();
+    this.attempt = null;
+  }
 };
 
-Miner.prototype.addTX = function addTX(tx) {
+Miner.prototype.createBlock = function createBlock(callback) {
+  var self = this;
+  var ts = Math.max(utils.now(), this.chain.tip.ts + 1);
+  var attempt;
+
+  // Find target
+  this.chain.getTargetAsync(this.chain.tip, ts, function(err, target) {
+    if (err)
+      return callback(err);
+
+    // Calculate version with versionbits
+    self.chain.computeBlockVersion(self.chain.tip, function(err, version) {
+      if (err)
+        return callback(err);
+
+      attempt = new MinerBlock({
+        tip: self.chain.tip,
+        version: version,
+        target: target,
+        address: self.address,
+        coinbaseFlags: self.coinbaseFlags,
+        segwit: self.chain.segwitActive,
+        dsha256: self.dsha256
+      });
+
+      if (!self.mempool)
+        return callback(null, attempt);
+
+      self.mempool.getSnapshot(function(err, hashes) {
+        if (err)
+          return callback(err);
+
+        utils.forEachSerial(hashes, function(hash, next) {
+          self.mempool.getTX(hash, function(err, tx) {
+            if (err)
+              return next(err);
+
+            self.mempool.fillAllCoins(tx, function(err) {
+              if (err)
+                return next(err);
+
+              attempt.addTX(tx);
+
+              next();
+            });
+          });
+        }, function(err) {
+          if (err)
+            return callback(err);
+
+          return callback(null, attempt);
+        });
+      });
+    });
+  });
+};
+
+Miner.prototype.mineBlock = function mineBlock(callback) {
+  var self = this;
+
+  // Create a new block and start hashing
+  this.createBlock(function(err, attempt) {
+    if (err)
+      return callback(err);
+
+    attempt.mineAsync(callback);
+  });
+};
+
+/**
+ * MinerBlock
+ */
+
+function MinerBlock(options) {
+  if (!(this instanceof MinerBlock))
+    return new MinerBlock(options);
+
+  this.options = options;
+  this.tip = options.tip;
+  this.height = options.tip.height + 1;
+  this.target = utils.fromCompact(options.target).toBuffer('le', 32);
+  this.extraNonce = new bn(0);
+  this.iterations = 0;
+  this.dsha256 = options.dsha256;
+
+  // Create a coinbase
+  this.coinbase = new bcoin.mtx();
+
+  this.coinbase.addInput({
+    prevout: {
+      hash: utils.toHex(constants.zeroHash),
+      index: 0xffffffff
+    },
+    coin: null,
+    script: new bcoin.script([
+      // Height (required in v2+ blocks)
+      bcoin.script.array(this.height),
+      // extraNonce - incremented when
+      // the nonce overflows.
+      bcoin.script.array(0),
+      // Add a nonce to ensure we don't
+      // collide with a previous coinbase
+      // of ours. This isn't really
+      // necessary nowdays due to bip34
+      // (used above).
+      bcoin.script.array(utils.nonce()),
+      // Let the world know this little
+      // miner succeeded.
+      new Buffer(options.coinbaseFlags, 'ascii')
+    ]),
+    witness: new bcoin.script.witness([]),
+    sequence: 0xffffffff
+  });
+
+  this.coinbase.addOutput({
+    address: options.address,
+    value: new bn(0)
+  });
+
+  // Create our block
+  this.block = new bcoin.block({
+    version: options.version,
+    prevBlock: this.tip.hash,
+    merkleRoot: constants.zeroHash,
+    ts: Math.max(utils.now(), this.tip.ts + 1),
+    bits: options.target,
+    nonce: 0
+  });
+
+  this.block.txs.push(this.coinbase);
+
+  if (options.segwit) {
+    // Set up the witness nonce and
+    // commitment output for segwit.
+    this.witness = true;
+    this.witnessNonce = utils.dsha256(new Buffer(this.tip.hash, 'hex'));
+    this.coinbase.inputs[0].witness.items[0] = this.witnessNonce;
+    this.coinbase.addOutput({
+      script: new bcoin.script([]),
+      value: new bn(0)
+    });
+  }
+
+  // Update coinbase since our coinbase was added.
+  this.updateCoinbase();
+
+  // Create our merkle root.
+  this.updateMerkle();
+}
+
+utils.inherits(MinerBlock, EventEmitter);
+
+MinerBlock.prototype.updateCommitment = function updateCommitment() {
+  var hash = this.block.getCommitmentHash();
+  this.coinbase.outputs[1].script = bcoin.script.createCommitment(hash);
+};
+
+MinerBlock.prototype.updateCoinbase = function updateCoinbase() {
+  this.coinbase.inputs[0].script[1] = this.extraNonce.toBuffer();
+  this.coinbase.outputs[0].value = this.block.getReward();
+};
+
+MinerBlock.prototype.updateMerkle = function updateMerkle() {
+  // Always update commitment before updating merkle root.
+  // The updated commitment output will change the merkle root.
+  if (this.witness)
+    this.updateCommitment();
+
+  this.block.ts = Math.max(utils.now(), this.tip.ts + 1);
+  this.block.merkleRoot = this.block.getMerkleRoot('hex');
+};
+
+MinerBlock.prototype.addTX = function addTX(tx) {
   var size = this.block.getVirtualSize() + tx.getVirtualSize();
 
   // Deliver me from the block size debate, please
@@ -197,206 +368,33 @@ Miner.prototype.addTX = function addTX(tx) {
   return true;
 };
 
-Miner.prototype.createBlock = function createBlock(callback) {
-  var self = this;
-  var ts = Math.max(utils.now(), this.chain.tip.ts + 1);
-  var coinbase, headers, block;
-
-  // Find target
-  this.chain.getTargetAsync(this.chain.tip, ts, function(err, target) {
-    if (err)
-      return callback(err);
-
-    // Calculate version with versionbits
-    self.chain.computeBlockVersion(self.chain.tip, function(err, version) {
-      if (err)
-        return callback(err);
-
-      // Create a coinbase
-      coinbase = bcoin.mtx();
-
-      coinbase.addInput({
-        prevout: {
-          hash: utils.toHex(constants.zeroHash),
-          index: 0xffffffff
-        },
-        coin: null,
-        script: new bcoin.script([
-          // Height (required in v2+ blocks)
-          bcoin.script.array(self.chain.height + 1),
-          // extraNonce - incremented when
-          // the nonce overflows.
-          bcoin.script.array(0),
-          // Add a nonce to ensure we don't
-          // collide with a previous coinbase
-          // of ours. This isn't really
-          // necessary nowdays due to bip34
-          // (used above).
-          bcoin.script.array(utils.nonce()),
-          // Let the world know this little
-          // miner succeeded.
-          new Buffer(self.coinbaseFlags, 'ascii')
-        ]),
-        witness: new bcoin.script.witness([]),
-        sequence: 0xffffffff
-      });
-
-      coinbase.addOutput({
-        address: self.address,
-        value: new bn(0)
-      });
-
-      // Create our block
-      headers = {
-        version: version,
-        prevBlock: self.chain.tip.hash,
-        merkleRoot: constants.zeroHash,
-        ts: ts,
-        bits: target,
-        nonce: 0
-      };
-
-      block = bcoin.block(headers);
-
-      block.txs.push(coinbase);
-
-      block.height = self.chain.height + 1;
-      block.target = utils.fromCompact(target).toBuffer('le', 32);
-      block.extraNonce = new bn(0);
-
-      if (self.chain.segwitActive) {
-        // Set up the witness nonce and
-        // commitment output for segwit.
-        block.witness = true;
-        block.witnessNonce = utils.nonce().toBuffer('le', 8);
-        coinbase.inputs[0].witness.items[0] = block.witnessNonce;
-        coinbase.addOutput({
-          script: new bcoin.script([]),
-          value: new bn(0)
-        });
-      }
-
-      // Update coinbase since our coinbase was added.
-      self.updateCoinbase(block);
-
-      // Create our merkle root.
-      self.updateMerkle(block);
-
-      return callback(null, block);
-    });
-  });
-};
-
-Miner.prototype.updateCommitment = function updateCommitment(block) {
-  var coinbase = block.txs[0];
-  var hash;
-
-  assert(coinbase);
-
-  if (!block)
-    block = this.block;
-
-  hash = block.getCommitmentHash();
-  coinbase.outputs[1].script = bcoin.script.createCommitment(hash);
-};
-
-Miner.prototype.updateCoinbase = function updateCoinbase(block) {
-  var coinbase = block.txs[0];
-
-  assert(coinbase);
-
-  if (!block)
-    block = this.block;
-
-  coinbase.inputs[0].script[1] = block.extraNonce.toBuffer();
-  coinbase.outputs[0].value = block.getReward();
-};
-
-Miner.prototype.updateMerkle = function updateMerkle(block) {
-  if (!block)
-    block = this.block;
-
-  // Always update commitment before updating merkle root.
-  // The updated commitment output will change the merkle root.
-  if (block.witness)
-    this.updateCommitment(block);
-
-  block.ts = Math.max(utils.now(), this.chain.tip.ts + 1);
-  block.merkleRoot = block.getMerkleRoot('hex');
-};
-
-Miner.prototype.iterate = function iterate() {
-  var self = this;
-
-  this.timeout = setTimeout(function() {
-    // Try to find a block: do one iteration of extraNonce
-    if (!self.findNonce())
-      return self.iterate();
-
-    // Add our block to the chain
-    self.chain.add(self.block, function(err) {
-      if (err) {
-        if (err.type === 'VerifyError')
-          utils.debug('%s could not be added to chain.', self.block.rhash);
-        self.emit('error', err);
-        return self.start();
-      }
-
-      // Emit our newly found block
-      self.emit('block', self.block);
-
-      // `tip` will now be emitted by chain
-      // and the whole process starts over.
-    });
-  }, 100);
-};
-
-Miner.prototype.__defineGetter__('hashes', function() {
-  return new bn(this.iterations).mul(utils.U32).addn(this.block.nonce);
-});
-
-Miner.prototype.__defineGetter__('rate', function() {
-  if (!this.block.nonce)
-    return 0;
-  // Calculate our terrible hashrate
-  return (this.block.nonce / (utils.now() - this._begin)) * 2 | 0;
-});
-
-Miner.prototype.sendStatus = function sendStatus() {
-  this.emit('status', {
-    block: this.block,
-    target: this.block.bits,
-    hashes: this.hashes.toString(10),
-    hashrate: this.rate,
-    height: this.chain.height + 1,
-    best: utils.revHex(this.chain.tip.hash)
-  });
-};
-
-Miner.prototype.findNonce = function findNonce() {
-  var data = this.block.abbr();
+MinerBlock.prototype.findNonce = function findNonce() {
+  var tip = this.tip;
+  var block = this.block;
+  var target = this.target;
+  var data = block.abbr();
   var now;
 
   // Track how long we've been at it.
-  this._begin = utils.now();
+  this.begin = utils.now();
 
-  assert(this.block.ts > this.chain.tip.ts);
+  assert(block.ts > tip.ts);
 
   // The heart and soul of the miner: match the target.
-  while (this.block.nonce <= 0xffffffff) {
+  while (block.nonce <= 0xffffffff) {
     // Hash and test against the next target
-    if (rcmp(this.dsha256(data), this.block.target) < 0)
+    if (rcmp(this.dsha256(data), target) < 0)
       return true;
 
     // Increment the nonce to get a different hash
-    this.block.nonce++;
+    block.nonce++;
 
     // Update the raw buffer (faster than
     // constantly serializing the block)
-    utils.writeU32(data, this.block.nonce, 76);
+    utils.writeU32(data, block.nonce, 76);
 
     // Send progress report every so often
-    if (this.block.nonce % 100000 === 0)
+    if (block.nonce % 100000 === 0)
       this.sendStatus();
   }
 
@@ -412,16 +410,16 @@ Miner.prototype.findNonce = function findNonce() {
   // performance because we do not have to
   // recalculate the merkle root.
   now = utils.now();
-  if (now > this.block.ts && now > this.chain.tip.ts) {
-    this.block.ts = now;
+  if (now > block.ts && now > tip.ts) {
+    block.ts = now;
     // Overflow the nonce
-    this.block.nonce = 0;
+    block.nonce = 0;
     return false;
   }
 
   // Overflow the nonce and increment the extraNonce.
-  this.block.nonce = 0;
-  this.block.extraNonce.iaddn(1);
+  block.nonce = 0;
+  block.extraNonce.iaddn(1);
 
   // We incremented the extraNonce, need to update coinbase.
   this.updateCoinbase();
@@ -432,6 +430,61 @@ Miner.prototype.findNonce = function findNonce() {
   return false;
 };
 
+MinerBlock.prototype.__defineGetter__('hashes', function() {
+  return new bn(this.iterations)
+    .mul(utils.U32)
+    .addn(this.block.nonce);
+});
+
+MinerBlock.prototype.__defineGetter__('rate', function() {
+  if (!this.block.nonce)
+    return 0;
+  // Calculate our terrible hashrate
+  return (this.block.nonce / (utils.now() - this.begin)) * 2 | 0;
+});
+
+MinerBlock.prototype.sendStatus = function sendStatus() {
+  this.emit('status', {
+    block: this.block,
+    target: this.block.bits,
+    hashes: this.hashes.toString(10),
+    hashrate: this.rate,
+    height: this.height,
+    best: utils.revHex(this.tip.hash)
+  });
+};
+
+MinerBlock.prototype.mine = function mine(callback) {
+  var self = this;
+
+  this.timeout = setTimeout(function() {
+    // Try to find a block: do one iteration of extraNonce
+    if (!self.findNonce())
+      return self.mine(callback);
+
+    return callback(null, self.block);
+  }, 100);
+};
+
+MinerBlock.prototype.mineSync = function mineSync() {
+  while (!this.findNonce());
+  return this.block;
+};
+
+MinerBlock.prototype.mineAsync = function mine(callback) {
+  return this.mine(callback);
+};
+
+MinerBlock.prototype.destroy = function destroy() {
+  clearTimeout(this.timeout);
+  this.timeout = null;
+  this.block = null;
+};
+
+/**
+ * Helpers
+ */
+
 function rcmp(a, b) {
   var i;
 
@@ -451,4 +504,6 @@ function rcmp(a, b) {
  * Expose
  */
 
-module.exports = Miner;
+exports = Miner;
+exports.minerblock = MinerBlock;
+module.exports = exports;
diff --git a/lib/bcoin/workers.js b/lib/bcoin/workers.js
index 3c9b4791..4ed3ac50 100644
--- a/lib/bcoin/workers.js
+++ b/lib/bcoin/workers.js
@@ -81,17 +81,21 @@ workers.call = function call(method, args, callback) {
   child = workers.alloc(id);
 
   function listener(err, result) {
-    clearTimeout(timeout);
-    timeout = null;
+    if (timeout) {
+      clearTimeout(timeout);
+      timeout = null;
+    }
     callback(err, result);
   }
 
   child.once(event, listener);
 
-  timeout = setTimeout(function() {
-    child.removeListener(event, listener);
-    return callback(new Error('Worker timed out.'));
-  }, workers.TIMEOUT);
+  if (method !== 'mine') {
+    timeout = setTimeout(function() {
+      child.removeListener(event, listener);
+      return callback(new Error('Worker timed out.'));
+    }, workers.TIMEOUT);
+  }
 
   child.stdin.write(createPacket(id, method, args));
 };
@@ -115,13 +119,25 @@ bcoin.tx.prototype.verifyAsync = function verifyAsync(index, force, flags, callb
   return workers.call('verify', [this, index, force, flags], callback);
 };
 
+bcoin.miner.minerblock.prototype.mineAsync = function mineAsync(callback) {
+  var attempt = {
+    tip: this.tip.toRaw(),
+    version: this.block.version,
+    target: this.block.bits,
+    address: this.options.address,
+    coinbaseFlags: this.options.coinbaseFlags,
+    segwit: this.options.segwit
+  };
+  return workers.call('mine', [attempt], callback);
+};
+
 /**
  * Child
  */
 
 workers.listen = function listen() {
   bcoin.debug = function debug() {
-    process.stderr.write('Worker ' + process.env.BCOIN_WORKER_ID + ':');
+    process.stderr.write('Worker ' + process.env.BCOIN_WORKER_ID + ': ');
     return console.error.apply(console.error, arguments);
   };
 
@@ -155,6 +171,28 @@ workers.verify = function verify(tx, index, force, flags) {
   return tx.verify(index, force, flags);
 };
 
+workers.mine = function mine(attempt) {
+  attempt = new bcoin.miner.minerblock({
+    tip: bcoin.chainblock.fromRaw(null, attempt.tip),
+    version: attempt.version,
+    target: attempt.target,
+    address: attempt.address,
+    coinbaseFlags: attempt.coinbaseFlags,
+    segwit: attempt.segwit,
+    dsha256: utils.dsha256
+  });
+  attempt.on('status', function(stat) {
+    utils.debug(
+      'hashrate=%dkhs hashes=%d target=%d height=%d best=%s',
+      stat.hashrate / 1000 | 0,
+      stat.hashes,
+      stat.target,
+      stat.height,
+      stat.best);
+  });
+  return attempt.mineSync();
+};
+
 /**
  * Helpers
  */