During 1983–1989, 49 moose (Alces alces) were monitored in central Sweden to estimate annual and seasonal home ranges. Males had larger annual home ranges (25.9 km2 ± 3.3 SE) than did females (13.7 km2 ± 2.2 SE, P < 0.01). Size of home ranges of males was strongly dependent on age (P < 0.05), in contrast to that of females (P < 0.20). We observed similar home-range sizes (10–20 km2) among younger male and female moose, whereas older males used larger home ranges than did older females, especially during autumn (P < 0.01) and winter (P < 0.01). Neither sex showed significant variation in home-range size among seasons (P > 0.05), except females without young (P < 0.05). Only in autumn did females with young have different (P < 0.01) average home-range size compared with females without young; those with young were, on average, twice as large as those without young (5.8 km2 versus 2.2 km2, respectively). We suggest that variation in home-range size may have two main causes. First, body size, and thus nutritional demands, varies between sexes throughout the year; second, the strong relationship between age and home-range size among males is likely caused by social activities associated with rut, and, in particular with age-related dominance.