Permeable pavements and similar stormwater control devices have not been exploited in the UK, in part because their adoption has been hindered by a lack of detailed knowledge of their hydrological performance. This paper describes a research programme that produced detailed information on the hydrological behaviour of a car park surface. The study involved the construction of full-scale permeable pavement model car park structures and a rainfall simulator for use in the laboratory. A monitoring procedure was developed in order to measure inputs and changes in drainage, storage and evaporation over short and long time-scales (2 hours to 3 months). A range of simulated rainfalls, which varied in intensity and duration, was applied to the model car park surfaces. Hydrological processes were monitored over an 18-month period. Results demonstrated that evaporation, drainage and retention in the structures were strongly in¯uenced by the particle size distribution of the bedding material and by water retention in the surface blocks. In general, an average of 55% of a one-hour duration, 15 mm h À1 rainfall event could be retained by an initially air-dry structure. Subsequent simulations demonstrated that 30% of a one-hour duration, 15 mm h À1 rainfall event could be stored by an initially wet structure (with a minimum time interval between rainfall applications of 72 hours).