Reviews existing methods for the prediction of infiltration rates and the factors influencing the pressure difference across buildings. Describes experimental procedure used in tests conducted in wind tunnel. Discusses results and presents prediction technique which enables surface pressures acting on aparticular building situated within an array of similar low rise buildings to be estimated, procedure takes account of the geometrical form of the building spacing parameters describing the array, direction of the wind and the upstream fetch conditions. The estimated value in the form of a pressure coefficient may be determined graphically. Includes data on gradient wind speed in the United Kingdom.