Background and objectives: Onchocerciasis is an important threat to public health in Nigeria, which in turn contributes significantly to total world cases of the disease. This study determined the rate of transmission of onchocerciasis in Ahani-Achi, identified the principal vector groups of the disease in the study area and evaluated the relative abundance of black fly vectors and the various transmission indices. Methodology: Black flies were caught using human baits and were assessed for parity. Parous flies were further dissected to detect the presence of Onchocerca larvae. Biting rates and transmission potentials were calculated using standard methods. Results: A total of 836 adult female flies were caught in the community. These were identified as members of the forest species of the S. damnosum complex. The differences in relative abundance between the months were not significantly different (P __ampersandsigngt; 0.05). The monthly biting rate (MBR) was lowest in February but highest in October. There was no on-going transmission in the area studied as no infective fly was caught. Hourly variation in fly activities were observed and this was significantly different (P__ampersandsignlt;0.01). Conclusions: The findings of this study signify that the forest black fly species are the major vectors of onchocerciasis in the area. Transmission in the study area is reduced but the presence of some larval stages of the filarial parasite in some flies signifies the possibility of transmission.