Indoor air flows induced by mechanical ventilation and air-conditioning (MVAC) systems are simulated by the technique of computational fluid dynamics (CFD). Examples are taken to illustrate the capability of the technique. These include the evaluation of basic ventilation system designs, ventilation systems in an enclosed car-park, spot cooling system, air-conditioning system with chilled ceiling, cold air distribution system. effect of casual heat gain on the air diffuser induced air flow and the underfloor air supply system. Evaluation of the performances of the mechanical systems in those buildings are performed. Physical experiments in air-conditioned spaces reported by Sakamoto and Matsuo; and by Murakami and Kato are also simulated to assess how good are the predicted results. (C) 2001 Elsevier Science Ltd. All rights reserved.