RXP is a validating parser written in C that creates a non-DOM tree representation of XML documents. While RXP itself is not well documented -- and not for the faint of heart -- at least two excellent higher level APIs have been built on top of RXP: pyRXP, a Python binding; and LT XML, a collection of utilities and libraries. In this article, David introduces you to RXP, compares it with the expat parser, and briefly discusses pyRXP and LT XML as ways of taking advantage of the speed RXP has to offer without all of its complexity.