An 18-month survey was performed of the anopheline mosquito fauna in the provincial town of Gambela, in a lowland savanna of western Ethiopia. The relative abundance and seasonal distribution of anthropophilic Anopheles species were remarkably similar to those reported for West African savanna regions. The climate, it should be noted, also was similar in both areas. All-night human bait captures and collections of indoor-resting forms suggested that, numerically, An. wellcomei was the most prevalent species, followed by An. funestus, An. gambiae, An. pharoensis, An. nili, and An. ziemanni; each (except An. gambiae and An. fiunestus) demonstrated strong exophilic resting behavior. The physiological condition of indoor resting An. funestus and An. gambiae suggested a deficit of pregravid and gravid forms, and significant temporal heterogeneity in the proportions of these relative to the totals. Less than expected frequencies of gravid females point to incipient outdoor resting behavior. Biting cycles of Anopheles are described. Month-specific sporozoite rates are given and their dynamics discussed. Maximum infection rates were observed late in wet seasons and minimum infection rates in the dry season. Mean annual sporozoite rates were 1.87% among An. gambiae, 1.23% for An. funestus, and 1.29% in An. nili. Estimated monthly man-biting densities of each of the 3 malaria vector species, multiplied by their sporozoite rates, suggested that risk to the average human inhabitant of acquiring malaria infection was greatest in the months of Sept.-Nov. The total numbers of potentially infective bites received by the average person was 10–12 per year in Gambela town and about 10 times these values in the smaller villages nearby.