VipTool is a tool for modelling, simulation, validation and verification of systems using place/transition Petri nets (p/t-nets). It implements the research done in a project named VIP (Verification of Information systems by evaluating partially-ordered Petri net runs) that was sponsored by the German Research Society (DFG). The main concern of this project is to establish a simulation and modelling concept for business processes given by Petri nets, which is based on the generation and evaluation of partially ordered execution runs (processes) instead of totally ordered sequences of transition occurrences. VipTool provides a comprehensive bundle of methods concerned with causality and concurrency modelled by partially ordered runs of p/t-nets. Namely, functionalities for synthesis, unfolding (combined with respective validation) and testing of executability are covered by VipTool.