A radio-tracking study of two adjacent social groups of red foxes was conducted in a suburban residential district of greater Toronto from late July through December 1990. This was the first radio-tracking study of red foxes living completely within a large metropolitan centre in North America. The groups had non-overlapping home ranges and included both breeding and non-breeding adult females. Mean group home range size was 52 ha, toward the small end of home ranges documented for the species, and distances travelled nightly by adults of both sexes ranged from 2-20 km. The home ranges of both groups were primarily located in a bushy ravine containing golf courses and park land, but individual foxes readily utilized areas of low-density housing characterized by large, well-vegetated lots. However, the foxes avoided adjacent medium-density housing areas, indicating that this population may not be as habituated to urban life as some populations described from Great Britain and mainland Europe. Because of their constant proximity to, and frequent use of, some residential habitat types, these foxes have ample opportunity to transmit diseases such as rabies to domestic pets and humans in the vicinity.