A survey of the prevalence of onchocerciasis was carried out in the Taraba river valley, Nigeria where Simulium damnosum s. l. is known to breed but about which no epidemiological data exists. Skin biopsies taken from 2,876 persons in 14 communities were examined for the microfilariae of Onchocerca volvulus. 100% infection rate was recorded in one of the communities, five other communities had prevalence rates between 81.0% and 94.7%. Three communities had infection rates between 44.8% and 69.1%. The mean microfilarial density in all the communities was 64.7 with a range between 3.2 and 167.6. The present findings indicate that the Taraba river valley may be one of the worst onchocerciasis zones in Nigeria.