The following document is namespace-invalid: <x xmlns:n1="http://www.w3.org" xmlns:n2="http://www.w3.org" > <!-- two attributes with the same name - this is namespace-invalid --> <bad n1:a="1" n2:a="2" /> </x> Crimson (the version included in JDK 1.4) doesn't reject it (when namespace processing is switched on). Michael Kay