The Unified Modelling Language (UML) is a standardised notation for describing object oriented software designs. We present vUML, a tool that automatically verifies UML models where the behaviour of the objects is described using UML Statecharts diagrams. The tool uses the SPIN model checker to perform the verification, but the user does not have to know how to use SPIN or the PROMELA language. If an error is found during the verification, the tool creates a UML sequence diagram showing how to reproduce the error in the model.