This paper describes the implementation of a debugger module for a programming language based on a process calculus. The language was used as a teaching tool for programming with message passing concurrent systems and in this context the development of a debugger for end users was of prime importance to increase usability of the system. We start by describing the syntax and semantics of the programming language and some programming examples. Then, we describe the implementation of the compiler and of the run-time system. Finally, we show how we can implement a debugger in a highly flexible way as a new module for the language.