A wind tunnel study was carried out to investigate the airflow through courtyard and atrium building models located within an urban setting and exposed to an urban atmospheric boundary layer. Ventilation strategies resulting from the use of different courtyard and atrium pressure regimes (positive pressure and suction) were examined. The model buildings were monitored both in isolation and in idealised urban environments of varying group layout densities. The effect of wind direction was also observed. The results from the study suggest that the open courtyard in an urban environment had a poor ventilation performance whilst an atrium roof with many openings operating under a negative (suction) pressure regime was the most effective. Changing the wind direction from perpendicular to the building facades to a 45 degrees incidence angle had the effect of making the differences in the observed flows between all the models much smaller. (C) 2001 Elsevier Science Ltd. All rights reserved.