The ecology (distribution, demography, habitat preferences and food habits) of five of the species of small mammals common to the Alberta Oil Sands are described – the species considered are Clethrionomys gapperi, Microtus pennsylvanicus, Peromyscus maniculatus, Tamiasciurus hudsonicus and Lepus americanus. The synthesis of available literature was restricted to these five species because these small mammals: 1. are abundant and widely distributed throughout .the AOSERP study area; 2. are important prey species of many furbearers and raptors; and 3. are potential pest species of afforestation programs in the AOSERP study area. Cyclic populations are typical for three of these species – C. gapperi and M. pennsylvanicus appear to undergo regular cycles in abundance once every three to four years whereas L. americanus appear to show regular 10-year cycles of abundance. P. maniculatus appear to undergo regular changes in density within each year but it is not clear if these species are cyclic over longer periods. T. hudsonicus population densities appear directly related to cone crop production. M. pennsylvanicus is rated as a major pest species of young afforestation areas. C. gapperi and L. americanus may also become major pest species as ground, shrub and tree cover increase. T. hudsonicus may cause severe damage to trees, particularly coniferous species, once tree cover is abundant and trees are producing seed. P. maniculatus damage is restricted to the consumption of tree and shrub seed – this is not thought to be a critical problem on afforestation areas in the AOSERP study areas in light of currently used afforestation techniques.