The gorillas studied at Bai Hokou, Central African Republic, between August 1990 and October 1992 consumed 239 kinds of foods from 138 species of plants and invertebrates, including the fruits of 77 species. Seeds were present in 99% of all fecal samples (n = 859). Although gorillas ate fleshy fruit whenever it was available, herbaceous plants and fibrous fruits were consumed year-round and were important during times of fleshy fruit scarcity. At Bai Hokou and across their range, resources are temporally discontinuous, and western gorilla diet exhibits marked seasonal and interannual variation. Although their large body size lends them dietary flexibility relative to chimpanzees, seasonal fruit-eating shapes the foraging and ranging patterns of western lowland gorillas. Am. J. Primatol. 43:87–109, 1997. © 1997 Wiley-Liss, Inc.