diff --git a/benchmark/index.html b/benchmark/index.html
index 4426db2..2733d31 100644
--- a/benchmark/index.html
+++ b/benchmark/index.html
@@ -16,6 +16,7 @@
       table { width: 48em; margin: 0 auto; border-spacing: 0; border-collapse: collapse; }
       table td, table th { border: 1px solid silver; padding: .25em 1em; }
       table td .unit { font-size: 75%; color: gray; }
+      table td.no-results  { padding: 1em; text-align: center; }
       table td.input-size  { text-align: right; }
       table td.parse-time  { text-align: right; }
       table td.parse-speed { text-align: right; }
@@ -27,11 +28,26 @@
       table tr.total td.parse-speed .value { font-size: 175%; }
 
       a, a:visited { color: #3d586c; }
+
+      #options {
+        width: 46em;
+        margin: 2em auto; border-radius: .5em; -moz-border-radius: .5em; padding: .5em 1em;
+        text-align: center;
+        background-color: #f0f0f0;
+      }
+      #options #run-count { width: 3em; }
+      #options #run { width: 5em; margin-left: 2em; }
     </style>
   </head>
   <body>
     <h1>PEG.js Benchmark Suite</h1>
 
+    <div id="options">
+      <label for="run-count">Run each test</label>
+      <input type="text" id="run-count" value="10"> times
+      <input type="button" id="run" value="Run">
+    </div>
+
     <table id="results-table">
       <tr class="columns">
         <th>Test</th>
@@ -39,6 +55,9 @@
         <th>Average Parse Time</th>
         <th>Average Parse Speed</th>
       </tr>
+      <tr>
+        <td class="no-results" colspan="4">No results available yet.</td>
+      </tr>
     </table>
 
     <script src="../lib/compiler.js"></script>
@@ -46,18 +65,6 @@
     <script src="../vendor/jquery/jquery.js"></script>
     <script src="../vendor/jquery.scrollto/jquery.scrollTo.js"></script>
     <script>
-      /*
-       * Each input is parsed |RUNS| times and the results are averaged. We do
-       * this for two reasons:
-       *
-       *   1. To warm up the interpreter (PEG.js-generated parsers will be most
-       *      likely used repeatedly, so it makes sense to measure performance
-       *      after warming up).
-       *
-       *   2. To minimize random errors.
-       */
-      var RUNS = 10;
-
       var benchmarks = [
         {
           id:          "json",
@@ -97,7 +104,7 @@
         }
       ];
 
-      $(document).ready(function() {
+      $("#run").click(function() {
         var resultsTable = $("#results-table");
 
         function appendHeading(heading) {
@@ -148,6 +155,27 @@
           }).responseText;
         }
 
+        /*
+         * Each input is parsed multiple times and the results are averaged. We
+         * do this for two reasons:
+         *
+         *   1. To warm up the interpreter (PEG.js-generated parsers will be
+         *      most likely used repeatedly, so it makes sense to measure
+         *      performance after warming up).
+         *
+         *   2. To minimize random errors.
+         */
+        var runCount = parseInt($("#run-count").val());
+        if (isNaN(runCount) || runCount <= 0) {
+          alert("Number of runs must be a positive integer.");
+          return;
+        }
+
+        $("#run-count, #run").attr("disabled", "disabled");
+
+        resultsTable.show();
+        $("#results-table tr").slice(1).remove();
+
         var totalInputSize = 0;
         var totalParseTime = 0;
 
@@ -169,12 +197,12 @@
             var input = get(url);
 
             var parseTime = 0;
-            for (var k = 0; k < RUNS; k++) {
+            for (var k = 0; k < runCount; k++) {
               var t = (new Date).getTime();
               parser.parse(input);
               parseTime += (new Date).getTime() - t;
             }
-            var averageParseTime = parseTime / RUNS;
+            var averageParseTime = parseTime / runCount;
 
             appendResult(
               "individual",
@@ -203,6 +231,12 @@
         appendResult("total", "Total", null, totalInputSize, totalParseTime);
 
         $.scrollTo("max", { axis: "y", duration: 500 });
+
+        $("#run-count, #run").removeAttr("disabled");
+      });
+
+      $(document).ready(function() {
+        $("#run").focus();
       });
     </script>
   </body>
