Introduction. Current tools and methods in architectural design do not allow predicting and evaluating how people will use designed environments before their actual realization. Objective. To investigate how computational simulation can help in evaluating design proposals as far as their use by people is concerned. Methods. Simulation of a medicine distribution procedure in a general hospital facility, while accounting for serendipitous social interactions made possible by the presence of different users in the same space, at the same time. Discussion. The simulation shows how use patterns are influenced by the social and physical context in which actors are situated, and demonstrates the significance of the proposed method of evaluating hospital designs before construction. The system allows simulating use patterns with different degrees of complexity, and enables architects to ask new types of questions related to the interactions between people and physical settings.