During a 13 month live-trapping study on a 2.3 ha grid located in upland coastal sage scrub near Irvine, California, the food habits of seven species of rodents were determined using fecal analysis. These included four cricetids, Reithrodontomys megalotis, Peromyscus maniculatus, P. eremicus, and P. calif omicus, and three heteromyids, Dipodomys agilis, Perognathus fallax, and P. longimembris. Laboratory feeding experiments using the cafeteria method in autumn 1971 indicated different patterns of food preference from wide acceptance of shrubs, forbs, and grasses (Dipodomys) to lower preferences for shrubs and high preferences for grasses (all cricetids except P. maniculatus) to relatively narrow acceptance of only grasses (P. longimembris). Comparison of diet composition by weight with volumetric percentages using fecal analysis of animals in feeding experiments indicated highest correlations for shrubs and forbs in cricetids and shrubs and grasses in heteromyids. Food habit trends revealed a high utilization of insects and Eriogonum fasciculatum by Reithrodontomys, a generalized diet for P. maniculatus, and a specialization on various seeds, flowers, and fruits by P. californicus and to a lesser degree by P. eremicus. The three heteromyids ate large amounts of annual and grass seeds during most months with the most opportunistic feeding shown by Dipodomys on grasses and forbs during winter-spring months. Food habits were most similar among the heteromyids, and P. eremicus-P. californicus. Of these, P. longimembris utilized winter torpor, whereas P. californicus was a seasonal resident. Food habit responses of subordinate cricetids to the spring immigration of P. californicus suggest the presence of both flexible feeding strategies and seasonally abundant resources in spring. These conditions may explain the continued coexistence of the diverse rodent fauna during this period.