Nine species of sympatric rain forest tree squirrels were studied in the field and in captivity at Makokou, Gabon. The findings on resource partitioning among them include: (1) two species are restricted to special habitat types. The other seven which commonly co—occur in the mature rain forest formation represent a maximum of taxonomic diversity. (2) Differential use of the vertical vegetation column divides these seven species into four essentially arboreal and three ground—foraging forms. (3) The species occupying a given foraging level and habitat differ in body size by approximately Hutchinson's ratio. Body size can act to partition fruit resources by size and hardness. (4) The squirrels are frugivores or omnivores; there are quantitative differences in diet between some species. These differences vary seasonally and may only be important during the most difficult season. (5) The four largest species have short active periods. I suggest that the greater species richness in African compared to Nearctic forests is permitted by a more constant productivity of fruit and arthropods, and a higher plant species diversity in the African forest.