A JavaScript object can be of great help when you need to pass multiple values to a Modal Window. E.G. var objArgs = new Object(); objArgs.Value1 = "Value 1"; objArgs.Value2 = 2; var modalWindowFeatures = 'dialogHeight:600px;dialogW... url = 'relative/path/to/page'; var returnValue; returnValue = window.showModalDialog(url,... );