The ventilation and leakage characteristics of suspended floors are not well documented. As part of a larger study of air flows in housing, the air flow through a suspended floor has been investigated under a number of conditions and methods of ventilation. The leakage of the suspended floor and the space beneath it has been measured and is compared with the house leakage. The infiltration to the underfloor space and also the infiltration to the house from the underfloor space through the suspended floor is investigated with natural ventilation and also with different modes of mechanical ventilation. The leakage of the underfloor space was varied to assess its influence on the ventilation characteristics of the suspended floor and hence on the air quality in the house. The results could also be of use in the investigation of infiltration of radon into dwellings with suspended floors.