Three species of microtine rodents occur near Atkasook Alaska: the brown lemming (Lemmus sibiricus), the collared lemming (Dicrostonyx torquatus), and the tundra vole (Microtus oeconomus). Population densities do not fluctuate as widely as do those of the brown lemming near Barrow, where densities may reach 200 ha-1. Differences with Barrow populations such as habitat preference, population density and food habits are described. Stomachs of brown lemmings mostly contained monocotyledons, particularly sedges and small amounts of mosses; collared lemmings mostly eat dicotyledon leaves, particularly willow, supplemented by small amounts of monocotyledons; and tundra voles eat large amounts of sedges, willows and a wide variety of herbaceous dicotyledons. None of the microtines eats the abundant, aromatic evergreen shrubs. Comparison of stomach contents with forage availability indicated strong food preferences. Palatability trials gave results consistent with these preferences, and many plants were not consumed. Microtines will consume rabbit pellets dosed with alcohol extracts of unpalatable plants. Feeding trials show that the most common sedge (Carex aquatilis) contains a compound(s) deleterious to collared lemmings, that the most common deciduous shrub (Salix pulchra) contains a compound(s) deleterious to brown lemmings, and that the most common aromatic shrub (Ledum palustre) contains a compound(s) deleterious to all 3 spp. of microtines. Apparently Lemmus and Dicrostonyx specialize on particular foods and cannot tolerate the secondary compounds in one another''s major food items; Microtus acts as a generalist whose food habits overlap with both lemmings. Competitive interactions between the vole and the lemmings may restrict the distribution of voles. Grazing pressure on graminoids exerted by microtine rodents at Atkasook is much less severe than at Barrow. Chronic damage to dicotyledons, particularly willow, is more widespread.