diff --git a/lodash.js b/lodash.js
index 9058b44a4..1252eb89c 100644
--- a/lodash.js
+++ b/lodash.js
@@ -28,6 +28,9 @@
   /** Used to generate unique IDs */
   var idCounter = 0;
 
+  /** Used to detect words composed of all capital letters */
+  var reAllCaps = /^[A-Z]+$/;
+
   /** Used to match empty string literals in compiled template source */
   var reEmptyStringLeading = /\b__p \+= '';/g,
       reEmptyStringMiddle = /\b(__p \+=) '' \+/g,
@@ -78,7 +81,7 @@
   var reUnescapedString = /['\n\r\u2028\u2029\\]/g;
 
   /** Used to match words to create compound words */
-  var reWords = /[A-Z]{2,}|[a-zA-Z0-9][a-z0-9]*/g;
+  var reWords = /[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[a-z]+|[0-9]+/g;
 
   /** Used to detect and test whitespace */
   var whitespace = (
@@ -6946,8 +6949,14 @@
      * _.camelCase('__hello_world__');
      * // => 'helloWorld'
      */
-    var camelCase = createCompounder(function(result, word, index) {
-      return result + word.charAt(0)[index ? 'toUpperCase' : 'toLowerCase']() + word.slice(1);
+    var camelCase = createCompounder(function(result, word, index, words) {
+      if (!index && reAllCaps.test(word)) {
+        return result + word.toLowerCase();
+      }
+      var lastWord = index && words[index - 1],
+          isCapped = index && !(index > 1 && words.length == 3 && (lastWord == 2 || lastWord == 4));
+
+      return result + (word.charAt(0)[isCapped ? 'toUpperCase' : 'toLowerCase']() + word.slice(1));
     });
 
     /**
diff --git a/test/test.js b/test/test.js
index 048f38730..e425d02e3 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1025,6 +1025,12 @@
       });
     });
 
+    test('`_.' + methodName + '` should handle double-converting strings', 4, function() {
+      _.forEach(['Hello world', 'helloWorld', '--hello-world', '__hello_world__'], function(string) {
+        equal(func(func(string)), expected);
+      });
+    });
+
     test('`_.' + methodName + '` should deburr letters', 1, function() {
       var actual = _.map(burredLetters, function(burred, index) {
         var isCamel = caseName == 'camel',
@@ -1059,6 +1065,25 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('lodash.camelCase');
+
+  (function() {
+    test('should work with numbers', 6, function() {
+      equal(_.camelCase('P2P'), 'p2p');
+      equal(_.camelCase('ascii 2 unicode'), 'ascii2unicode');
+      equal(_.camelCase('two 4 one'), 'two4one');
+      equal(_.camelCase('walk 500 miles'), 'walk500Miles');
+      equal(_.camelCase('xhr2 request'), 'xhr2Request');
+      equal(_.camelCase('too legit 2 quit'), 'tooLegit2Quit');
+    });
+
+    test('should handle acronyms', 1, function() {
+      equal(_.camelCase('XMLHttpRequest'), 'xmlHttpRequest');
+    });
+  }());
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('lodash.capitalize');
 
   (function() {