diff --git a/CHANGELOG.md b/CHANGELOG.md
index d6d400b66..f2c442050 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Current Master
 
+- Add a check for improper Transaction data.
+
 ## 2.13.5 2016-10-18
 
 - Increase default max gas to `100000` over the RPC's `estimateGas` response.
diff --git a/app/scripts/lib/inpage-provider.js b/app/scripts/lib/inpage-provider.js
index c6bfdb4da..052a8f5fe 100644
--- a/app/scripts/lib/inpage-provider.js
+++ b/app/scripts/lib/inpage-provider.js
@@ -84,7 +84,7 @@ MetamaskInpageProvider.prototype.send = function (payload) {
     // throw not-supported Error
     default:
       var link = 'https://github.com/MetaMask/faq/blob/master/DEVELOPERS.md#dizzy-all-async---think-of-metamask-as-a-light-client'
-      var message = `The MetaMask Web3 object does not support synchronous methods like ${payload.method}. See ${link} for details.`
+      var message = `The MetaMask Web3 object does not support synchronous methods like ${payload.method} without a callback parameter. See ${link} for details.`
       throw new Error(message)
 
   }
diff --git a/test/unit/util_test.js b/test/unit/util_test.js
index 45e545e8e..00528b905 100644
--- a/test/unit/util_test.js
+++ b/test/unit/util_test.js
@@ -227,5 +227,27 @@ describe('util', function() {
         assert.equal(result.toString(10), '1111000000000000000', 'accepts decimals')
       })
     })
+    describe('#isHex', function(){
+      it('should return true when given a hex string', function() {
+        var result = util.isHex('c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2')
+        assert(result)
+      })
+
+      it('should return false when given a non-hex string', function() {
+        var result = util.isHex('c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714imnotreal')
+        assert(!result)
+      })
+
+      it('should return false when given a string containing a non letter/number character', function() {
+        var result = util.isHex('c3ab8ff13720!8ad9047dd39466b3c%8974e592c2fa383d4a396071imnotreal')
+        assert(!result)
+      })
+
+      it('should return true when given a hex string with hex-prefix', function() {
+        var result = util.isHex('0xc3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2')
+        assert(result)
+      })
+
+    })
   })
 })
diff --git a/ui/app/send.js b/ui/app/send.js
index 97ed29e4a..b8af19028 100644
--- a/ui/app/send.js
+++ b/ui/app/send.js
@@ -7,6 +7,7 @@ const actions = require('./actions')
 const util = require('./util')
 const numericBalance = require('./util').numericBalance
 const addressSummary = require('./util').addressSummary
+const isHex = require('./util').isHex
 const EthBalance = require('./components/eth-balance')
 const ethUtil = require('ethereumjs-util')
 const RangeSlider = require('./components/range-slider')
@@ -190,7 +191,7 @@ SendTransactionScreen.prototype.render = function () {
           marginBottom: '16px',
         },
       }, [
-        'Transactional Data (optional)',
+        'Transaction Data (optional)',
       ]),
 
       // 'data' field
@@ -312,6 +313,11 @@ SendTransactionScreen.prototype.onSubmit = function (gasPrice) {
     return this.props.dispatch(actions.displayWarning(message))
   }
 
+  if (!isHex(ethUtil.stripHexPrefix(txData)) && txData) {
+    message = 'Transaction data must be hex string.'
+    return this.props.dispatch(actions.displayWarning(message))
+  }
+
   this.props.dispatch(actions.hideWarning())
 
   var txParams = {
diff --git a/ui/app/util.js b/ui/app/util.js
index e4b77e2bc..7a56bf6a0 100644
--- a/ui/app/util.js
+++ b/ui/app/util.js
@@ -35,6 +35,7 @@ module.exports = {
   normalizeNumberToWei: normalizeNumberToWei,
   valueTable: valueTable,
   bnTable: bnTable,
+  isHex: isHex,
 }
 
 function valuesFor (obj) {
@@ -209,3 +210,7 @@ function readableDate (ms) {
   var time = `${hours}:${minutes.substr(-2)}:${seconds.substr(-2)}`
   return `${dateStr} ${time}`
 }
+
+function isHex (str) {
+  return Boolean(str.match(/^(0x)?[0-9a-fA-F]+$/))
+}