Historically, much effort in the process engineering industry and in related academic projects has concentrated on the representation and solution of either full flowsheet models or individual unit operations. More recently, there have been significant advances in representing such mathematical modelling information more declaratively. In this paper, three key criticisms are made concerning the systems currently available for the purpose of process modelling. The structure of a new environment that addresses these, three criticisms is described. This environment uses agents as its basic elements. A prototype of the environment has been implemented and two example problems that have been used to illustrate this implementation are presented. These examples show how agents are used in the system both as representations for physical, mathematical and numerical entities and as active implementing elements which both formulate and solve the required models.