This study examined habitat use and diet composition of Norwegian lemmings (Lemmus lemmus) and field voles (Microtus agrestis), which occur together and potentially compete for resources in alpine areas of central Norway. Both species preferred habitats rich in herbaceous monocots and dicots and willow (meadows and willow meadows). However, lemmings spread into other habitats, particularly lichen heath, when populations were high. Lemmings showed a clear preference for monocots in their diet, eating mostly sedges (Carex and Eriophorum), whereas voles had a much more diverse diet that included equal amounts of, and more species of, monocots and dicots. Because relatively little overlap occurred either in habitat use (33–57%, increasing overlap with lower densities of lemmings) or in diet (30–51%), and because lemming populations were usually low, exploitative competition between the 2 species seemed unlikely. Nevertheless, aggressive interspecific interactions during occasional years with high lemming densities could still negatively influence populations of field voles.