A number of computer models for the evacuation of buildings have been produced in recent years. These models typically use a system known as network-node modelling, which makes a number of large assumptions concerning human motion. Methods used in the software package SIMULEX differ from the traditional methods of assessing motion in terms of average parameters and flow rates . The most significant feature of the model is the geometrically accurate simulation of the evacuation movement of each individual person from a building space. The algorithms which achieve this movement are not based on any standard method of evacuation modelling, so it is important to assess how realistic the algorithms prove to be, and also to investigate the performance of the system as a whole.This paper describes a series of tests in which SIMULEX models the movement of a large group of people through a number of exits of different widths. The maximum sustainable flow rates that were achieved in the tests are presented and compared to data from different sources. The application of SIMULEX to the proposed design of a large commercial store is also discussed.