diff --git a/xdoc/plugin.jelly b/xdoc/plugin.jelly
index d3aad866..3b93b540 100644
--- a/xdoc/plugin.jelly
+++ b/xdoc/plugin.jelly
@@ -440,7 +440,21 @@
             <!-- generate output file name -->
             <util:replace var="outFileForward" oldChar="\" newChar="/" value="${file.toString()}"/>
             <j:set var="outFile" value="${mapper.mapFileName(outFileForward).0}"/>
-    
+
+        <j:set var="varname" value="up${file.toString()}"/>
+        <uptodate
+          property="${varname}"
+          srcfile="${file.toString()}"
+          targetfile="${outFile.toString()}" />
+
+        <j:set var="speedup" value="${maven.xdoc.skip.uptodate}"/>
+       <j:choose>
+           <j:when test="${context.getVariable(varname) and speedup.equals('true')}">
+               <!-- <echo>${outFile} is up to date.</echo>  -->
+           </j:when>
+           <j:otherwise>
+
+
             <echo>Generating ${outFile} from ${file}</echo>
             <!-- work out relative path -->
             <util:replace var="docsForward" oldChar="\" newChar="/" value="${srcdir}"/>
@@ -479,6 +493,10 @@
               prettyPrint="no">
               <j:include uri="${stylesheet.toString()}"/>
             </j:file>
+
+           </j:otherwise>
+       </j:choose>
+
           </j:forEach>
 
      </util:available>
diff --git a/xdoc/plugin.properties b/xdoc/plugin.properties
index 3e3a7ded..2ce6da7c 100644
--- a/xdoc/plugin.properties
+++ b/xdoc/plugin.properties
@@ -84,6 +84,8 @@ maven.xdoc.copy.excludes.classic=external-classic.png,help_logo.gif,icon_arrowfo
 # Note that navigation.xml and ${maven.xdoc.xml.copy} are included implicitly
 maven.xdoc.validate.exclude=changes.xml
 
+maven.xdoc.skip.uptodate=false
+
 #
 # I18N Preferences
 #
diff --git a/xdoc/xdocs/changes.xml b/xdoc/xdocs/changes.xml
index 563a6f2a..15acf798 100644
--- a/xdoc/xdocs/changes.xml
+++ b/xdoc/xdocs/changes.xml
@@ -27,6 +27,7 @@
   </properties>
   <body>
     <release version="1.10" date="in SVN">
+      <action dev="ltheussl" type="add" issue="MPXDOC-141" due-to="M. Sean Gilligan">Perform JSL transforms on xdocs <strong>only</strong> when they have changed.</action>
       <action dev="ltheussl" type="add" issue="MPXDOC-169">Add xdoc tag library documentation to the plugin site.</action>
       <action dev="ltheussl" type="fix" issue="MPXDOC-87">Fix <code>xdoc:validate</code>.</action>
       <action dev="ltheussl" type="fix" issue="MPXDOC-106" due-to="Jerome Lacoste">One cannot call xdoc:copy-user-resources directly.</action>
diff --git a/xdoc/xdocs/properties.xml b/xdoc/xdocs/properties.xml
index bb2e2ff4..9de961af 100644
--- a/xdoc/xdocs/properties.xml
+++ b/xdoc/xdocs/properties.xml
@@ -61,6 +61,15 @@
             <code>${maven.build.dir}/generated-xdocs</code>.
           </td>
         </tr>
+      </table>
+    </section>
+    <section name="Performance Properties">
+      <table>
+        <tr>
+          <th>Property name</th>
+          <th>Optional?</th>
+          <th>Description</th>
+        </tr>
         <tr>
           <td>maven.xdoc.xml.copy</td>
           <td>Yes</td>
@@ -102,6 +111,22 @@
             <code>changes.xml</code>.
           </td>
         </tr>
+        <tr>
+          <td>maven.xdoc.skip.uptodate</td>
+          <td>Yes</td>
+          <td>
+            If set to <code>true</code>, Maven compares the timestamps
+            of corresponding source- and generated files and only
+            performs a transformation if they are different.
+            This leads to a speedup of the site generation by eliminating
+            tranforms of unchanged documents. <strong>Note</strong>:
+            this only applies to user-supplied source documents, if you
+            change settings in <code>project.xml</code>, <code>navigation.xml</code>
+            or any other properties- or configuration file, you should
+            generate the site from scratch to make sure all cross-links
+            are correct. Defaults to <code>false</code>.
+          </td>
+        </tr>
       </table>
     </section>
     <section name="Localization Properties">

Property name	Optional?	Description
maven.xdoc.xml.copy	Yes
maven.xdoc.skip.uptodate	Yes	+ If set to `true`, Maven compares the timestamps + of corresponding source- and generated files and only + performs a transformation if they are different. + This leads to a speedup of the site generation by eliminating + tranforms of unchanged documents. Note: + this only applies to user-supplied source documents, if you + change settings in `project.xml`, `navigation.xml` + or any other properties- or configuration file, you should + generate the site from scratch to make sure all cross-links + are correct. Defaults to `false`. +