Studies on the anthropophilic blackflies in the Gilgel Ghibe area with reference to therntransmission of onchocerciasis were conducted between April 1994 and March 1995.rnThe results of this study showed that onchocerciasis was of low endemicity in the area.rnParasitologically positive skin snips were recorded for 17.1% of the persons examined. Thernprevalence of infection in males (19%) was higher than in females (14.9%). The geometric meanrnnumber of microfilariae per skin snip was 11.14, and was higher in males than in females. Clinicalrnsigns and symptoms were observed in 26.3% of the population examined- itching (18.4%),rnpigmentary changes (3.5%), itching with pigmentary changes (3.07%) and itching with papular rashrn(1.3%). The collection of biting flies at four selected sites revealed Simulium damnosurn complex tornbe the predominant anthropophilic species in the locality followed by S. ethiopiense which appearedrnin very small numbers.. Dissections of 6,483 S. damnoSum complex showed an average parous rilternof 74.7%. The parous rate was observed to vary between the four sites. Parous rates of 87.8%,rn62.4%, 56.9% and 41.4% were recorded at sites I, 2, 3 and 4lespectively, suggesting a differentialrndispersal of parous and nulliparous flies. Of the total 4,844 parous flies dissected, 1.8% werernharbouring L3 larvae morphologically indistinguishable from Q. volvulus. The average number ofrnL3 Q. volvulus per fly was 5.1. The infection rate at the different sites was, 2.32% (Site 1 ), 0.75%rn(Site 2), 0.97% (Site 3) and 2.98% (Site 4). The annual biting rate (ABR), the annual infective biting rate (AIBR) and the annual transmission potential (A TP) was,24,928.75, 328.7 and 1,669.5 respectively. Of the total 5 specimens of-.S.. ethiopiense 60% (3) were parous and none of these wererninfected. The species plays little or no role in the transmission of onchocerciasis in the Gilgel Ghibe area.