We present a Petri net semantics for the Business Process Execution Language for Web Services (BPEL). Our semantics covers the standard behaviour of BPEL as well as the exceptional behaviour (e.g. faults, events, compensation). The semantics is implemented as a parser that translates BPEL specifications into the input language of the Petri net model checking tool LoLA. We demonstrate that the semantics is well suited for computer aided verification purposes.