Hi list, here's what I have: poc.xml: <?xml version="1.0" encoding="utf-8" ?> <myrootnode> <myns:mynode xmlns:myns="http.//www.example.com/myns"> <myns:mysubnode>some text</myns:mysubnode> </myns:mynode> </myrootnode> poc.py: #!/usr/bin/env python from lxml import etree DocTree = etree.parse("poc.xml") QueryResult = DocTree.xpath("//myns:mynode") The result (with added version info): [gentop][scel@/home/scel/workspace/lxmlbug] > ./poc.py lxml.etree: (1, 2, 1, 0) libxml used: (2, 6, 27) libxml compiled: (2, 6, 27) libxslt used: (1, 1, 17) libxslt compiled: (1, 1, 17) Traceback (most recent call last): File "./poc.py", line 9, in ? QueryResult = DocTree.xpath("//myns:mynode") File "etree.pyx", line 1256, in etree._ElementTree.xpath File "xpath.pxi", line 75, in etree._XPathEvaluatorBase.evaluate File "xpath.pxi", line 212, in etree.XPathDocumentEvaluator.__call__ File "xpath.pxi", line 105, in etree._XPathEvaluatorBase._handle_result File "xpath.pxi", line 93, in etree._XPathEvaluatorBase._raise_parse_error etree.XPathSyntaxError: error in xpath expression The expression however, is valid (or I'm just insanely stupid). I tested the same query on the same data using http://dmag.upf.edu/contorsion/query.jsp and it worked just as it should. Strangely, //*[name()='myns:mynode'] works with lxml. Regards, Torsten -- Torsten Rehn <scel@users.sourceforge.net>