Field measurements in the crawl spaces of multistorey buildings showed these to be satisfactorily ventilated. In eight of nine buildings the air exchange rates of the crawl spaces were 0.3- 1.1 l/s per square metre of crawl space area. In one of the buildings the crawl space was totally unventilated. Crawl space air temperatures varied from 9-14 deg C in winter to 15-22 deg C in late summer. Condensation occurred occasionally or throughout the year on the foundation base walls or lower surface of the floor in six buildings. Evaporation of moisture from the crawl space ground was the most important factor affecting the crawl space climate. According to the results it is impossible to control effectively the air humidity in a crawl space solely by ventilation of the crawl space.