The overall air leakage of high-rise buildings cannot be measured using a full pressure method because of the large volume involved. Describes a method of conducting small-scale pressurization tests on the exterior walls of apartments in multi-storey buildings. Gives results of measurements in a test building. compares direct method with values obtained by summing the air leakage of individual components. Finds good agreement. Concludes that floor/wall joints, windows and window sills are the three major air leakage sources in exterior walls.