Abstract. The purpose of this contribution is to give an overview of constructions and results for Petri net transformations in the Petri Net Baukasten developed by the "DFG-Forschergruppe Petrinetz-Technologie". The two main concepts of Petri net transformations considered in this context are net class and net model transformations. In both cases we present first the relevance of transformations in the application developer view and them the technical constructions and results in the expert view of the Petri Net Baukasten . Net class transformations are transformations between different Petri net classes, like elementary nets, place/transition nets and algebraic high-level nets. Net model transformations on the other hand are transformations of the net structure for nets within one Petri net class, like place or transition refinement. The main technical results are concerning the preservation of safety resp. liveness properties of net model transformations and compatibility results between net class and net model transformations. The relevance of the constructions and results for the application developer view is demonstrated by a small case study modeling the interaction of a buffer, a printer and a communication unit consisting of secure and non-secure channels. Finally we give an overview of other concepts of transformations: On one hand, transformations between Petri nets and other system modeling techniques, and on the other hand transformations between different net representation formats using XML-schemes and DTD-standards.