Studies of woodland caribou (Rangifer tarandus caribou) in the Birch Mountains of northeastern Alberta were conducted during January 1976-June 1978; 29 caribou were radio-collared and located 1,001 times from fixed-wing aircraft. A population survey combining fixed-wing, transect flights and helicopter tracking yielded a late-winter density of 1 caribou/24 km2 over 1,400 km2. Adult bulls concentrated on this area in winter; adjusted resident density was 1/32 km2. Bulls comprised 46% of animals older than calves. Calves made up 12% of the total fall and winter population. Yearlings comprised 14% of 35 captured caribou during 1976-77, but individuals born during 1972-74 comprised only 15%. Radio-collared cows calved from 7 May to 2 June. Calf survival was 42% in the 1st 2 months of life; annual survival of 27 radio-collared adults averaged 85%. Composition of caribou groups changed conspicuously throughout the year. Caribou group sizes were smallest in summer (x̄ = 1.2) and largest in late fall after the rut (x̄ = 5.4). Seasonal ranges and movement patterns varied greatly among individuals, but seemed traditional among adult bulls. The latter made "long-distance" movements (> 11 km) up to 5 times per year to distinct seasonal ranges. Most cows moved 2 and sometimes 3 times per year. Seasonal range sizes were similar for bulls and cows, but individual cows were more sedentary and their seasonal ranges overlapped more. Mean annual range size of adult bulls was 1,196 km2, and that of cows was 539 km2. Seasonal changes in relative use of habitat types seemed related to availability of food, snow depths, and social behavior. Most locations (69%) were in lowland cover, predominantly black spruce (Picea mariana) muskegs.