The thermal environment of both natural and artificial burrows of Dipodomys spectabilis was moderate as compared to surface ambient conditions but was related to them. Burrow air temperatures were similar to, but not identical with, soil temperatures. Burrow humidity was generally near saturation and was related to both burrow temperature and surface ambient humidity. CO2 concentration in kangaroo rat burrows was variable but was always higher than ambient. Burrow CO2 concentration resulted from a complex of factors that included soil moisture and temperature and proximity of an animal. Surface wind velocity probably plays an important role in burrow ventilation. Burrow structure and soil characteristics influence environmental conditions of burrows.