diff --git a/lib/yuidoc.js b/lib/yuidoc.js
index 3d354047..80519338 100755
--- a/lib/yuidoc.js
+++ b/lib/yuidoc.js
@@ -245,8 +245,48 @@ YUI.add('yuidoc', function (Y) {
             }
         },
 
+        /**
+         * Applies preprocessors to the data tree. 
+         * This function first clones the data and operates on the clone. 
+         * @method runPreprocessors
+         * @private
+         * @return {Object} The mutated data
+         */
+        runPreprocessors: function (data) {
+            var self = this,
+                preprocessors,
+                preprocessorsRelativeTo;
+
+            // We will try to load the preprocessors as npm modules, but we will also 
+            // search for them relative to the process working directory.
+            // The latter is consistent with how other paths are treated by yuidoc, 
+            // such as the config options 'paths' and 'outdir'.
+            preprocessorsRelativeTo = process.cwd();
+
+            if (self.options.preprocessor) {
+                data=JSON.parse(JSON.stringify(data));
+
+                preprocessors = [].concat(self.options.preprocessor);
+
+                preprocessors.forEach(function (preprocessor) {
+                    var preprocessorModule;
+
+                    try {
+                        preprocessorModule = require(preprocessor);
+                    } catch (e) {
+                        preprocessorModule = require(path.resolve(preprocessorsRelativeTo, preprocessor));
+                    }
+
+                    preprocessorModule(data, self.options);
+                });
+            }
+
+            return data;
+        },
+
         /**
          * Writes the parser JSON data to disk.
+         * Applies preprocessors, if any.
          * @method writeJSON
          * @param {Object} parser The DocParser instance to use
          * @private
@@ -262,6 +302,8 @@ YUI.add('yuidoc', function (Y) {
 
             data.warnings = parser.warnings;
 
+            data = this.runPreprocessors(data);
+
             if (self.selleck && self.options.selleck && data.files && data.modules) {
                 Object.keys(self.selleck).forEach(function (file) {
                     Object.keys(data.files).forEach(function (f) {
diff --git a/package.json b/package.json
index e16856aa..50ef23b9 100644
--- a/package.json
+++ b/package.json
@@ -49,7 +49,7 @@
     },
     "scripts": {
         "pretest": "jshint ./lib/*.js ./tests/*.js",
-        "test": "istanbul cover --print=both --yui ytestrunner -- --include ./tests/options.js --include ./tests/builder.js --include ./tests/parser.js --include ./tests/parser_coffee.js --include ./tests/files.js --include ./tests/utils.js"
+        "test": "istanbul cover --print=both --yui ytestrunner -- --include ./tests/options.js --include ./tests/builder.js --include ./tests/parser.js --include ./tests/parser_coffee.js --include ./tests/files.js --include ./tests/utils.js --include ./tests/preprocessor.js"
     },
     "preferGlobal": "true",
     "licenses":[
diff --git a/scripts/test.sh b/scripts/test.sh
index 94ffe494..6839f92a 100755
--- a/scripts/test.sh
+++ b/scripts/test.sh
@@ -19,7 +19,8 @@ wait
     ./builder.js \
     ./options.js \
     ./utils.js \
-    ./files.js
+    ./files.js \
+    ./preprocessor.js
 
 exit $?
 
diff --git a/tests/input/preprocessor/preprocessortest.js b/tests/input/preprocessor/preprocessortest.js
new file mode 100644
index 00000000..314fec3c
--- /dev/null
+++ b/tests/input/preprocessor/preprocessortest.js
@@ -0,0 +1,5 @@
+/**
+ * This class is for testing the preprocessor option.
+ * @class TestPreprocessor
+ * @customtag hello
+ */
diff --git a/tests/lib/testpreprocessor.js b/tests/lib/testpreprocessor.js
new file mode 100644
index 00000000..09bbf011
--- /dev/null
+++ b/tests/lib/testpreprocessor.js
@@ -0,0 +1,14 @@
+module.exports=function(data, options) {
+	var star="*";
+
+	if (options.star)
+		star=options.star;
+
+	global.testPreprocessorCallCount++;
+
+	for (className in data.classes) {
+		classData=data.classes[className];
+
+		classData.customtagPlusStar=classData.customtag+star;
+	}
+}
diff --git a/tests/lib/testpreprocessormodule/package.json b/tests/lib/testpreprocessormodule/package.json
new file mode 100644
index 00000000..e00fa501
--- /dev/null
+++ b/tests/lib/testpreprocessormodule/package.json
@@ -0,0 +1,3 @@
+{
+	"main": "./testpreprocessormodule.js"
+}
diff --git a/tests/lib/testpreprocessormodule/testpreprocessormodule.js b/tests/lib/testpreprocessormodule/testpreprocessormodule.js
new file mode 100644
index 00000000..001e814c
--- /dev/null
+++ b/tests/lib/testpreprocessormodule/testpreprocessormodule.js
@@ -0,0 +1,3 @@
+module.exports=function(data) {
+	data.testModuleWasHere=true;
+}
diff --git a/tests/preprocessor.js b/tests/preprocessor.js
new file mode 100644
index 00000000..ab78ea68
--- /dev/null
+++ b/tests/preprocessor.js
@@ -0,0 +1,101 @@
+/*global Y:true */
+var YUITest = require('yuitest'),
+    Assert = YUITest.Assert,
+    path = require('path'),
+    fs = require('fs'),
+    Y = require(path.join(__dirname, '../', 'lib', 'index'));
+
+//Move to the test dir before running the tests.
+process.chdir(__dirname);
+
+var suite = new YUITest.TestSuite({
+    name: 'Preprocessor Test Suite',
+    setUp: function () {
+        process.chdir(__dirname);
+    }
+});
+
+suite.add(new YUITest.TestCase({
+    name: "Preprocessor",
+    'test: single preprocessor': function () {
+        global.testPreprocessorCallCount=0;
+
+        var json = (new Y.YUIDoc({
+            quiet: true,
+            paths: ['input/preprocessor'],
+            outdir: './out',
+            preprocessor: 'lib/testpreprocessor.js'
+        })).run();
+
+        Assert.isObject(json);
+        Assert.areSame(global.testPreprocessorCallCount,1,"the preprocessor was not called");
+    },
+    'test: single preprocessor with absolute path': function () {
+        global.testPreprocessorCallCount=0;
+
+        var json = (new Y.YUIDoc({
+            quiet: true,
+            paths: ['input/preprocessor'],
+            outdir: './out',
+            preprocessor: path.join(process.cwd(),'/lib/testpreprocessor.js')
+        })).run();
+
+        Assert.isObject(json);
+        Assert.areSame(global.testPreprocessorCallCount,1,"the preprocessor was not called when an absolute path was used");
+    },
+    'test: several preprocessors': function () {
+        global.testPreprocessorCallCount=0;
+
+        var json = (new Y.YUIDoc({
+            quiet: true,
+            paths: ['input/preprocessor'],
+            outdir: './out',
+            preprocessor: ['lib/testpreprocessor.js','./lib/testpreprocessor']
+        })).run();
+
+       Assert.isObject(json);
+       Assert.areSame(global.testPreprocessorCallCount,2,"the preprocessor was not called twice");
+    },
+    'test: the test preprocessor does its job': function () {
+        var json = (new Y.YUIDoc({
+            quiet: true,
+            paths: ['input/preprocessor'],
+            outdir: './out',
+            preprocessor: 'lib/testpreprocessor.js',
+            star: "#"
+        })).run();
+
+        Assert.isObject(json);
+        Assert.areSame(json.classes.TestPreprocessor.customtagPlusStar,"hello#","the preprocessor did not modify the data");
+    },
+    'test: load preprocessor as a npm module': function () {
+        // We are testing if it works to load the preprocessor from node_modules,
+        // so first we need to copy it in place.
+        if (!fs.existsSync("../node_modules/testpreprocessormodule")) {
+            fs.mkdirSync("../node_modules/testpreprocessormodule");
+        }
+
+        fs.writeFileSync("../node_modules/testpreprocessormodule/package.json",
+            fs.readFileSync("lib/testpreprocessormodule/package.json"));
+
+        fs.writeFileSync("../node_modules/testpreprocessormodule/testpreprocessormodule.js",
+            fs.readFileSync("lib/testpreprocessormodule/testpreprocessormodule.js"));
+
+        var json = (new Y.YUIDoc({
+            quiet: true,
+            paths: ['input/preprocessor'],
+            outdir: './out',
+            preprocessor: 'testpreprocessormodule'
+        })).run();
+
+        Assert.isObject(json);
+        Assert.isTrue(json.testModuleWasHere,"the preprocesor module was not run");
+
+        // Clean up things when we are done.
+        fs.unlinkSync("../node_modules/testpreprocessormodule/package.json");
+        fs.unlinkSync("../node_modules/testpreprocessormodule/testpreprocessormodule.js");
+        fs.rmdirSync("../node_modules/testpreprocessormodule");
+    }
+}));
+
+YUITest.TestRunner.add(suite);