A synthesis of the published literature on the habitat preferences of beavers, muskrats, mink and river otters is presented. Field studies conducted during the late autumn of 1978 included aerial surveys and track counts in snow. A total of 249 active beaver lodges were seen on 2550 km of transects. Densities of active beaver lodges were calculated from surveys of streams and lakes to be lodge per 3.1 km of stream and 1 lodge per 7.2 km of lakeshore. A total of 26 muskrat houses were seen on three lakes within the AOSERP study area. The Peace-Athabasca Delta was not surveyed. Beavers used deciduous, white spruce and willow-fen habitats proportionately more than these habitats were available. Beavers avoided locating their lodges in jack pine and black spruce-tamarack habitats. Tracks of mink were found to occur in greater numbers in willow and aspen vegetation types than would be expected by the availability of these habitats. Habitat preferences of muskrats and river otters could not be determined because too few data were collected on these species. Recommendations for habitat management that would benefit semi-aquatic furbearers are made.