In this paper, we have presented FrameKit, a software platform dedicated to the rapid prototyping of CASE environment. FrameKit architecture is similar to the ECMA reference model. It focuses on the quick definition of new graphical representations, handled by a generic user interface. FrameKit also contains a development kit composed of program libraries in various languages (C, Ada and Unix shell). This eases both the implementation and integration of new tools. FrameKit also has good capabilities to integrate software components that were not especially designed for it. FrameKit is operational and we have used it to build the CPN-AMI 2.0 CASE environment that implements a design methodology for distributed systems. To achieve it, we had to describe three formalisms (one is hierarchical) and register the services of a dozen tools. The first version, released on Internet in the first quarter of 1997 () is quite satisfactory. We plan to enrich it with new mechanisms to ease the quick design of code generators as well as model simulators.