We determined the feeding habits, including seasonal and annual variations in diet composition, of the Jalapan pine vole (Microtus quasiater), an endemic rodent from Mexico. During 3 annual cycles, feces were collected on a monthly basis from a population located in a mountain cloud forest at Apulco, Puebla, Mexico. Microscope slides were prepared from each fecal sample, and fragments of food items were identified by comparison with photomicrographic references. Thirty-six plant species occurred in the diet, representing more than 60% of the identified plant species in our study area. Roots, sedge heads, seeds, dicotyledonous flowers, and fungi each contributed less than 10% of the diet. This rodent consumed 85% of the monocotyledonous species present in the area, but only 50% of the dicotyledonous species. The diet showed seasonal and yearly differences. M. quasiater remained highly selective in its diet.