Studies were conducted in the Nile Delta of Egypt to determine the feasibility of detecting Wuchereria bancrofti microfilariae (Mf) in mosquitoes as a primary surveillance method for the identification of filariasis-endemic villages. Initial experimental studies evaluated the ingestion, survival, and migration rates of W. bancrofti Mf in Culex pipiens and Culex antennatus after mosquitoes were fed on infected volunteers. In 2 villages, 1,684 bloodfed mosquitoes were dissected during the night immediately after collections inside houses. In the village of Kafr Tahoria, Mf were found in 27 of 519 Cx. pipiens and in one of 8 Anopheles pharoensis. In Tahoria, Mf were detected in 7 of 799 Cx. pipiens and in one of 302 Cx. antennatus. Identifying filariasis-endemic villages based on the detection of Mf in mosquitoes may be a useful strategy for epidemiologic studies or for filariasis control programs.