This paper presents a methodology and a tool box for system-level partitioning in the behavioral domain. The methodology is based on an extended finite state machine model. Partitioning is achieved interactively through the application of five system-level transformation primitives: MOVE, MERGE, SPLIT, CUT and MAP. This scheme allows an interactive exploration of the solution space. The result of the partitioning is a set of interconnected and heterogeneous sub-systems. The partitioning tool box which has been developed is named PARTIE PARTIF includes an evaluation feedback loop that helps the designer estimate the quality of the design.