diff --git a/ScriptInterpreter.js b/ScriptInterpreter.js
index 27a217e..d1992c7 100644
--- a/ScriptInterpreter.js
+++ b/ScriptInterpreter.js
@@ -119,7 +119,10 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
           case OP_14:
           case OP_15:
           case OP_16:
-            this.stack.push(bigintToBuffer(opcode - OP_1 + 1));
+            var opint = opcode - OP_1 + 1;
+            var opbuf = bigintToBuffer(opint);
+            console.log('op'+opcode+' = '+opint+', '+buffertools.toHex(opbuf));
+            this.stack.push(opbuf);
             break;
 
           case OP_NOP:
@@ -352,8 +355,6 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
           case OP_SIZE:
             // (in -- in size)
             var value = bignum(this.stackTop().length);
-            //var topSize = util.bytesNeededToStore(castBigint(this.stackTop()).toNumber());
-            //var value = bignum(topSize);
             this.stack.push(bigintToBuffer(value));
             break;
 
@@ -396,6 +397,10 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
             // (x1 x2 - bool)
             var v1 = this.stackTop(2);
             var v2 = this.stackTop(1);
+            console.log('equal');
+            console.log(v1);
+            console.log(v2);
+
             var value = buffertools.compare(v1, v2) === 0;
 
             // OP_NOTEQUAL is disabled because it would be too easy to say
@@ -476,6 +481,9 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
             // (x1 x2 -- out)
             var v1 = castBigint(this.stackTop(2));
             var v2 = castBigint(this.stackTop(1));
+            console.log('add');
+            console.log(v1);
+            console.log(v2);
             var num;
             switch (opcode) {
               case OP_ADD:
@@ -874,7 +882,6 @@ var castBigint = ScriptInterpreter.castBigint = function castBigint(v) {
   if (!v.length) {
     return bignum(0);
   }
-
   // Arithmetic operands must be in range [-2^31...2^31]
   if (v.length > 4) {
     throw new Error("Bigint cast overflow (> 4 bytes)");
@@ -883,46 +890,55 @@ var castBigint = ScriptInterpreter.castBigint = function castBigint(v) {
   var w = new Buffer(v.length);
   v.copy(w);
   w = buffertools.reverse(w);
-  if (w[0] & 0x80) {
-    w[0] &= 0x7f;
-    return bignum.fromBuffer(w).neg();
+  console.log('v ='+buffertools.toHex(w));
+  var isNeg = w[0] & 0x80;
+  if (isNeg) {
+    for (var i = 0; i<w.length; i++) {
+      console.log('before = '+w[i]);
+      w[i] = ~w[i];
+      console.log('after  = '+w[i]);
+    }
+    console.log('w ='+buffertools.toHex(w));
+    return bignum.fromBuffer(w).add(bignum(1)).neg();
   } else {
-    // Positive number
     return bignum.fromBuffer(w);
   }
 };
+
+var padSign = function(b) {
+  var c;
+  if (b[0] & 0x80) {
+    c = new Buffer(b.length + 1);
+    b.copy(c, 1);
+    c[0] = 0;
+  } else {
+    c = b;
+  }
+  return c;
+}
+
 var bigintToBuffer = ScriptInterpreter.bigintToBuffer = function bigintToBuffer(v) {
   if ("number" === typeof v) {
     v = bignum(v);
   }
-
   var b, c;
-
   var cmp = v.cmp(0);
   if (cmp > 0) {
+    console.log('positive');
     b = v.toBuffer();
-    if (b[0] & 0x80) {
-      c = new Buffer(b.length + 1);
-      b.copy(c, 1);
-      c[0] = 0;
-      return buffertools.reverse(c);
-    } else {
-      return buffertools.reverse(b);
-    }
+    c = padSign(b);
+    c = buffertools.reverse(c);
   } else if (cmp == 0) {
-    return new Buffer([]);
+    c = new Buffer([]);
   } else {
+    console.log('negative '+v);
     b = v.neg().toBuffer();
-    if (b[0] & 0x80) {
-      c = new Buffer(b.length + 1);
-      b.copy(c, 1);
-      c[0] = 0x80;
-      return buffertools.reverse(c);
-    } else {
-      b[0] |= 0x80;
-      return buffertools.reverse(b);
-    }
+    console.log(b);
+    c = padSign(b);
+    c = Util.negativeBuffer(c);
+    c = buffertools.reverse(c);
   }
+  return c;
 };
 
 ScriptInterpreter.prototype.getResult = function getResult() {
diff --git a/test/test.ScriptInterpreter.js b/test/test.ScriptInterpreter.js
index 01777dd..9dfd47e 100644
--- a/test/test.ScriptInterpreter.js
+++ b/test/test.ScriptInterpreter.js
@@ -2,6 +2,7 @@
 
 var chai = chai || require('chai');
 var bitcore = bitcore || require('../bitcore');
+var buffertools = require('buffertools');
 
 var should = chai.should();
 var testdata = testdata || require('./testdata');
@@ -22,6 +23,19 @@ describe('ScriptInterpreter', function() {
     var si = new ScriptInterpreter();
     should.exist(si);
   });
+  var data = [
+    [0, ''],
+    [1, '01'],
+    [-1, 'ff'],
+  ];
+  data.forEach(function(datum) {
+    var i = datum[0];
+    var hex = datum[1];
+    it('bigintToBuffer should work for ' + i, function() {
+      var result = ScriptInterpreter.bigintToBuffer(i);
+      buffertools.toHex(result).should.equal(hex);
+    });
+  });
   var i = 0;
   testdata.dataScriptValid.forEach(function(datum) {
     if (datum.length < 2) throw new Error('Invalid test data');
@@ -34,7 +48,7 @@ describe('ScriptInterpreter', function() {
       ScriptInterpreter.verify(Script.fromHumanReadable(scriptSig),
         Script.fromHumanReadable(scriptPubKey),
         null, 0, 0, // tx, output index, and hashtype
-        function (err, result) {
+        function(err, result) {
           should.not.exist(err);
           result.should.equal(true);
           done();
@@ -67,8 +81,3 @@ describe('ScriptInterpreter', function() {
  
 
 });
-
-
-
-
-
diff --git a/test/test.examples.js b/test/test.examples.js
index 4115bc7..55c9ccd 100644
--- a/test/test.examples.js
+++ b/test/test.examples.js
@@ -15,8 +15,8 @@ var examples = [
 ];
 
 describe('Examples', function() {
-  before(mute);
-  after(unmute);
+  //before(mute);
+  //after(unmute);
   examples.forEach(function(example) {
     it('valid '+example, function() {
       var ex = require('../examples/'+example);
diff --git a/test/test.util.js b/test/test.util.js
index 8e5c504..6edda6e 100644
--- a/test/test.util.js
+++ b/test/test.util.js
@@ -99,6 +99,8 @@ describe('util', function() {
       [4294967295, 'ffffffff00'],
       [4294967296, '0000000001'],
       [4294967297, '0100000001'],
+      [2147483647, 'ffffff7f'],
+      [-2147483647, '01000080'],
       //[-4294967295, 'feffffffffffffff'],
       //[-4294967296, 'feffffffffffffff'],
       //[-4294967297, 'feffffffffffffff'],
diff --git a/util/util.js b/util/util.js
index a31c9f1..1732682 100644
--- a/util/util.js
+++ b/util/util.js
@@ -98,7 +98,7 @@ var formatBuffer = exports.formatBuffer = function (buffer, maxLen) {
 
 var valueToBigInt = exports.valueToBigInt = function (valueBuffer) {
   if (Buffer.isBuffer(valueBuffer)) {
-    return bignum.fromBuffer(valueBuffer, {endian: 'little', size: 8});
+    return bignum.fromBuffer(valueBuffer, {endian: 'little', size: 'auto'});
   } else {
     return valueBuffer;
   }
@@ -108,16 +108,10 @@ var bigIntToValue = exports.bigIntToValue = function (valueBigInt) {
   if (Buffer.isBuffer(valueBigInt)) {
     return valueBigInt;
   } else {
-    return valueBigInt.toBuffer({endian: 'little', size: 8});
+    return valueBigInt.toBuffer({endian: 'little', size: 'auto'});
   }
 };
 
-var intTo64Bits = function(integer) {
-  return { 
-    hi: Math.floor(integer / 4294967296),
-    lo: (integer & 0xFFFFFFFF) >>> 0
-  };
-};
 var fitsInNBits = function(integer, n) {
   // TODO: make this efficient!!!
   return integer.toString(2).replace('-','').length < n;
@@ -127,6 +121,21 @@ exports.bytesNeededToStore = bytesNeededToStore = function(integer) {
   return Math.ceil(((integer).toString(2).replace('-','').length + 1)/ 8);
 };
 
+exports.negativeBuffer = negativeBuffer = function(b) {
+  // implement two-complement negative
+  var c = new Buffer(b.length);
+  // negate each byte
+  for (var i=0; i<b.length; i++){
+    c[i] = ~b[i];
+  }
+  // add one
+  for (var i=b.length - 1; i>=0; i--){
+    c[i] += 1;
+    if (c[i] !== 0) break;
+  }
+  console.log('negative of '+buffertools.toHex(b)+' is '+buffertools.toHex(c));
+  return c;
+}
 
 exports.intToBuffer = function(integer) {
   var size = bytesNeededToStore(integer);
@@ -139,27 +148,15 @@ exports.intToBuffer = function(integer) {
     if (si.lenght === 1) {
       si = '0' + si;
     }
-    buf.word8((neg?-1:1)*parseInt(si, 16));
+    buf.word8(parseInt(si, 16));
   }
-  return buf.buffer();
-
-  var data = null;
-  if (fitsInNBits(integer, 8)) {
-    data = new Buffer(1);
-    data.writeInt8(integer, 0);
-  } else if (fitsInNBits(integer, 16)) {
-    data = new Buffer(2);
-    data.writeInt16LE(integer, 0);
-  } else if (fitsInNBits(integer, 32)) {
-    data = new Buffer(4);
-    data.writeInt32LE(integer, 0);
-  } else {
-    var x = intTo64Bits(integer);
-    data = new Buffer(8);
-    data.writeInt32LE(x.hi, 0); // high part contains sign information (signed)
-    data.writeUInt32LE(x.lo, 4); // low part encoded as unsigned integer
+  var ret = buf.buffer();
+  if (neg) {
+    ret = buffertools.reverse(ret);
+    ret = negativeBuffer(ret);
+    ret = buffertools.reverse(ret);
   }
-  return data;
+  return ret;
 };
 
 var formatValue = exports.formatValue = function (valueBuffer) {