The present study develops a System which explains resultant data (drug prescriptions) in terms of causal measures (doctor behaviour) and enables Management to set strategic plans, to control and evaluate them. The system of the present study is composed of a series of "Models" such as doctor behaviour communication, doctor behaviour and sales man models. Each model represents the process which Management believes goes on within that segment of a Marketing activity. The Simulation Based Information System developed for two french drug companies becomes therefore a test market without memory in which Management may examine with impunity the complications of alternative policies and strategies in the whole pharmaceutical market. Whether introducing new drug or considering modification of a marketing program, in the doctor or salesman sector, management may apply alternative strategies in the simulated environment and evaluate their implications under various assured competitors conditions.