The paper describes a prototype system for the automatic generation of a mathematical model, describing the dynamic behavior of a process system, from a purely physical description. A synthetic approach is adopted, in which models are built up using a library of physico-chemical laws. Essentially a process is modelled as a collection of interacting phases, with various kinds of interaction or transfer between them, together with additional relations expressing containment and control. A prototype package, at present limited to the generation of lumped-parameter models, has demonstrated the feasibility of the approach.