A population of mountain pygmy-possums Burramys parvus was studied at the Mount Blue Cow ski resort in Kosciuszko National Park between 1986 and 1989. Forty-eight individuals were radiotracked during the snow-free months and 21 individuals were tracked during winter over the 3 years of study. Trapping and radiotracking showed that the density, population structure, movements and home range sizes of B. parvus on Mount Blue Cow were strongly correlated with elevation and changed with the season. Female densities were greatest in habitats characterized by deep boulderfields, at high elevations with an abundance of Bogong moths. Males visited the areas where females were located to breed in November–December and then by February, the majority migrated to lower elevations or north and westerly aspects. Females that nested at lower elevations also visited high-elevation habitats to access the high concentrations of Bogong moths, which were the main food source in summer. A high proportion of the juvenile males and some juvenile females dispersed to lower elevations in March and April. The resulting sexual segregation during autumn and winter may be a result of female aggression or scramble competition, but is also explainable by differences in energy requirements, seed availability and hibernation strategies between the sexes. The extraordinarily large nightly and seasonal movements between habitat patches of up to 2 km for females and 3 km for males, sexual segregation and the use of different hibernation sites have important implications for the management of this species. These include the need for movement and dispersal corridors and the conservation of boulder-heath habitats outside the main boulderfields.