Engineering individual components of a multi-agent system and their interactions is a complex and error-prone task in urgent need of methods and tools. Prototyping is a valuable technique to help software engineers explore the design space while gaining insight and a “feel” for the dynamics of the system; prototyping also allows engineers learn more about the relationships among design features and the desired computational behaviour. In this paper we describe an approach to building prototypes of large multi-agent systems with which we can experiment and analyse results. We have implemented an environment embodying our approach. This environment is supported by a distributed platform that helps us achieve controlled simulations.