I confirm the presence of a serious memory leak in ElementTree, using the iterparse() function.
Memory grows disproportionately to dozens of GB when parsing a large XML file.

For further information, see discussion in:
  http://www.gossamer-threads.com/lists/python/bugs/912164?do=post_view_threaded#912164
but notice that the comments attributing the problem to the OS are quite off the mark.

To replicate the problem, try this on a Wikipedia dump:

    iterparse = ElementTree.iterparse(file)
    id = None
    for event, elem in iterparse:
        if elem.tag.endswith("title"):
            title = elem.text
        elif elem.tag.endswith("id") and not id:
            id = elem.text
        elif elem.tag.endswith("text"):
           print id, title, elem.text[:20]