The annual diet of 110 Mazama pocket gophers (Thomomys mazama) collected in the pine region of south-central Oregon [USA] during 1973-74 consisted mainly of the aboveground parts of forbs (40%), grasses (32%) and woody plants (4%). Plant roots comprised 24% of the diet. Food availability was an important determinant of diet. Vegetation on the study area was about 1/3 grasses and 2/3 forbs. Annual forbs comprised 87% of the total forb cover. The diets of gophers collected during the growing season, July-Sept., did not differ significantly, but diets during other sampling periods did (P < 0.05). Succulent forbs were preferred to all other plants, but they were not abundant enough to provide a dependable food supply. Grasses were consumed most heavily during the dormant season when annual forbs were not available. Woodly plants, including ponderosa pine (Pinus ponderosa), were eaten in winter, but they constituted only a minor portion of the diet. [Pocket gophers feed on conifer seedlings and may hinder or prevent reforestation in the Pacific Northwest.].