Sixty-one Culicoides spp. were collected in Kenya, Uganda and Tanzania between January 1966 and December 1967 using light-traps at 35 stations on a NW-SE transect from the Indian Ocean to central Uganda to evaluate the distribution of Culicoides spp. among ecological zones. Most species were confined to one or at least very few similar habitats. The largest number of species (30) occurred in the forest zone, probably because of the many suitable breeding sites, whereas only three species were recorded from the dry bushland zone. Forests also contained more exclusive Culicoides spp., whereas savanna species showed a wider distribution, suggesting that the forest species are less adaptable than others. The disease vectors C. grahamii Aust. and C. pallidipennis C, I. & M. were among the most abundant and widely distributed species.