A study of small mammal populations (small rodents and snowshoe hares), habitat use, small rodent diets, and small mammal damage in natural forest and successional communities was begun in June 1978 and continued until November 1979. Based on population sizes and distributions, four species of small mammals, Clethrionomys gapperi, Microtus pennsylvanicus, Peromyscus maniculatus, and Lepus americanus, were determined to be important components of the boreal forest ecosystem in northeastern Alberta. Twelve additional species of small mammals were captured during this program but numbers were small. Indices of habitat quality based on peak population sizes, responses to habitat structure, habitat preferences, an index of dispersal, reproductive activity, and nutritional condition indicated that balsam poplar forests and young successional areas were high quality habitats for most small rodents, whereas black spruce and tamarack forests were marginal. In contrast, black spruce communities were near-optimal habitats for L. americanus, and balsam poplar forests were only moderately well-suited. Feeding habits of C. gapperi, M. pennsylvanicus, and P. maniculatus in this study were similar to diets described previously in other studies. Lichens, Carex spp., and arthropods were the major foods for each species, respectively. Mycorrhiza were consumed regularly by all species. Bark tissue of trees and shrubs was found most frequently in C. gapperi diets, but was limited in diets of M. pennsylvanicus. Consumption of bark by P. maniculatus, previously unreported in the literature, was common during the spring and fall. Damage to trees and shrubs in natural and successional areas by small rodents was limited. In contrast, browsing by snowshoe hares was high in some communities, notably tamarack forests. Some species of trees and shrubs were highly susceptible to damage, whereas others were resistant. Some factors associated with local variation in amounts of small mammal damage are discussed.