diff --git a/docs/UsersManual.html b/docs/UsersManual.html
index 4ba00e0..5c5f6f9 100644
--- a/docs/UsersManual.html
+++ b/docs/UsersManual.html
@@ -36,6 +36,7 @@
    <ul>
    <li><a href="#diagnostics_display">Controlling How Clang Displays Diagnostics</a></li>
    <li><a href="#diagnostics_mappings">Diagnostic Mappings</a></li>
+   <li><a href="#diagnostics_categories">Diagnostic Categories</a><li>
    <li><a href="#diagnostics_commandline">Controlling Diagnostics via Command Line Flags</a></li>
    <li><a href="#diagnostics_pragmas">Controlling Diagnostics via Pragmas</a></li>
    </ul>
@@ -417,9 +418,9 @@
 <li>An option that indicates how to control the diagnostic (for diagnostics that
     support it) [<a 
    href="#opt_fdiagnostics-show-option">-fdiagnostics-show-option</a>].</li>
-<li>A high-level category for the diagnostic for clients that want to group
-    diagnostics by class (for diagnostics that
-    support it) [<a 
+<li>A <a href="#diagnostics_categories">high-level category</a> for the
+    diagnostic for clients that want to group diagnostics by class (for
+    diagnostics that support it) [<a 
    href="#opt_fdiagnostics-show-category">-fdiagnostics-show-category</a>].</li>
 <li>The line of source code that the issue occurs on, along with a caret and
     ranges that indicate the important locations [<a
@@ -435,6 +436,7 @@
 <p>For more information please see <a href="#cl_diag_formatting">Formatting of
 Diagnostics</a>.</p>
 
+
 <h4 id="diagnostics_mappings">Diagnostic Mappings</h4>
 
 <p>All diagnostics are mapped into one of these 5 classes:</p>
@@ -448,7 +450,23 @@
 <li>Fatal</li>
 </ul></p>
 
-<h4 id="diagnostics_commandline">Controlling Diagnostics via Command Line Flags</h4>
+<h4 id="diagnostics_categories">Diagnostic Categories</h4>
+
+<p>Though not shown by default, diagnostics may each be associated with a
+   high-level category.  This category is intended to make it possible to triage
+   builds that produce a large number of errors or warnings in a grouped way.
+</p>
+
+<p>Categories are not shown by default, but they can be turned on with the
+<a href="#opt_fdiagnostics-show-category">-fdiagnostics-show-category</a> option.
+When set to "<tt>name</tt>", the category is printed textually in the diagnostic
+output.  When it is set to "<tt>id</tt>", a category number is printed.  The
+mapping of category names to category id's can be obtained by running '<tt>clang
+  --print-diagnostic-categories</tt>'.
+</p>
+
+<h4 id="diagnostics_commandline">Controlling Diagnostics via Command Line
+ Flags</h4>
 
 <p>-W flags, -pedantic, etc</p>