The interiors of Ethiopian mud and grass dwellings were treated with a space repellent, Deet (N, N diethyl-m-toluamide), and the resultant effects on mosquito behavior assessed. Significant alterations in host finding, resting, and feeding behavior of Anopheline and Culicine mosquitoes were observed for 3 weeks after treatment. The potential use of "dwelling space repellents" in malaria control schemes is discussed.