Human IgG antibodies against Plasmodium falciparum asexual stages, gametocytes and sporozoites were detected by indirect fluorescent antibody (IFA) techniques in the blood meals of Anopheles gambiae s.l. from a malaria-endemic area of western Kenya. Field-collected mosquitoes, which had been stored dry for over 2 years, were screened first for human IgG by ELISA. In 141 blood meal samples from human-fed mosquitoes, the prevalence of stage-specific antibodies was 87.9% for asexual-stage parasites, 78.0% for gametocytes, and 87.9% for sporozoites. There were no differences in the prevalence of stage-specific antibodies for mosquitoes collected from 2 sites, before and after the long rainy season of 1988. The detection of specific human antibodies in mosquito blood meals by IFA, or by more efficient methods, may provide alternative approaches for large-scale, epidemiologic studies of malaria and other vector-borne diseases.