||Architects are often faced with the problem to assess how their design decisions will affect the behaviour of individuals. Various performance indicators are related to the behaviour of individuals in particular environments. One approach to deal with this problem is to develop a system that relates user behaviour to design parameters.The paper discusses the framework of a multi-agent system approach for investigating visualized simulated pedestrian activity and behaviour within a building. The approach will lead to a system that may serve as a toolkit in the design process for a better understanding what the design look like, and perhaps more importantly have users will behave in that particular environment. Agent technology is derived from DAI which is also applied in the construction industry (Onuegbu O. Ugwu e.a., The application of DAI in the construction industry, CIT2000, pp. 959-970).The concept of this system is based on micro-simulation of pedestrian flows and multi-agent technology. In this context, pedestrians are people navigating within the built environment. The system simulates how agents move around in a particular 3D environment, in which space is represented as a network which is a lattice of cells with local states, subject to a uniform set of rules, which drives the behaviour of the system. Agents represent pedestrians with their own behaviour, moving over the network. The 3D environment is a virtual environment of the design of a new building or the revitalization of an existing building. Thus, a virtual building environment with virtual pedestrians will be constructed using multi-agent simulation. In this particular environment, a set of instances corresponding to the elements of multi-agent simulations is designed. We distinguish user-agents that represent pedestrians in the simulation. We call the individual that is supposed to walk through the environment a subject-agent and all other simulated pedestrians in the system actor-agents. Thus, subject-agent and actor-agents are user-agents that navigate in this virtual environment, each with their own behaviour, beliefs and intentions.With the simulation system, we will get more insight into the pedestrian activity behaviour and thus in the pedestrian flows in buildings, not yet existing. This will be of great importance in the assessment of design performance. For a designer or researcher, this system approach results in a decision support tool for the early stages in the design process of the construction of a building.