XML database functionality has been emerging in "XML-only" databases as well as in the major relational database products. Yet, there is no industry standard XML database benchmark to evaluate alternative implementations. The research community has proposed several benchmarks which are all useful in their respective scope, such as evaluating XQuery processors. However, they do not aim to evaluate a database system in its entirety and do not represent all relevant characteristics of a real-world XML application. Often they only define read-only single-user tests on a single XML document. We have developed an application-oriented and domain-specific benchmark called "Transaction Processing over XML" (TPoX). It exercises all aspects of XML databases, including storage, indexing, logging, transaction processing, and concurrency control. Based on our analysis of real XML applications, TPoX simulates a financial multi-user workload with XML data conforming to the FIXML standard. In this paper we describe TPoX and present early performance results. We also make its implementation publicly available.