We investigated fungal consumption and resulting patterns of potential spore dispersal by 6 small mammals in old-growth habitat in the Sierra Nevada of the United States, a region in which this ecological interrelationship is poorly understood. Small mammals consumed a wide array of food items, although only feces of northern flying squirrels (Glaucomys sabrinus), golden-mantled ground squirrels (Spermophilus lateralis), and Douglas squirrels (Tamiasciurus douglassi) frequently contained spores of hypogeous fungi, whereas those of lodgepole chipmunks (Tamias speciosus), long-eared chipmunks (T. quadrimaculatus), and deer mice (Peromyscus maniculatus) did so rarely. Feces from the 3 squirrel species also contained a greater number of hypogeous fungal genera per sample than did samples from the latter 3 species. Flying squirrels potentially dispersed the greatest variety of ectomycorrhizal fungi (16 genera): 8 in spring and 15 in autumn. Frequency of occurrence of 9 genera in the feces of flying squirrels differed between spring and autumn. Interspecific differences in patterns of fungal consumption, coupled with differences among these small mammals in habitat use, mobility, and digestive physiology, suggest that these small mammals may disperse fungi in ecologically nonredundant ways and that the integrity of entire small-mammal communities may be important to the maintenance of ectomycorrhizal diversity in coniferous forests.