Design/CPN is a tool package supporting the use of Coloured Petri Nets (also known as CP-nets or CPN). It has three integrated parts: The CPN Editor supports construction, modification and syntax check of CPN models. The CPN Simulator supports interactive and automatic simulation of CPN models. The Occurrence Graph Tool supports construction and analysis of occurrence graphs for CPN models (also known as state spaces or reachability graphs/trees). The simulator and the occurrence graph tool are both implemented in the functional language ML. Furthermore, the tool language itself (the inscription language) is ML.