Formal methods, techniques and tools are, at the present time, an active research topic in different areas of computer science (knowledge representation, real-time systems, algorithms, etc.). These formal techniques are intended to help users specify consistently their needs and verify them. Only mathematical techniques are able to prove or to verify the coherence of the specification of a given system or algorithm, etc. However, there is an enormous difficulty to out into use the mathematical techniques and concepts. This difficulty stems from the fact that these mathematical techniques and concepts are accessible only by a minority of specialists. To solve this problem, we have to develop tools and methods to help users to make the most out of formal approaches, without the apparent complexity of mathematical problems. This paper presents a tool, called CAST (Computer-Aided Specification Tool) dedicated to help users specify communicating processes and systems in concurrent engineering environments. CAST Is a graphical tool which provides a friendly user interface. At the present time, CAST allows users to specify design processes by representing them in the form of automata and provides an SCCS (Synchronous Calculus of Communicating Systems) specification. This tool Is developed in the SHOOD project which aims at providing tools and methods for the integration of engineering design systems.