Salivary glands were removed from female mosquitoes of laboratory-reared strains of species common to southern Florida. Protein antigens were isolated from homogenates of these glands by denaturing electrophoresis and transferred to nitrocellulose for immunoblotting with serum samples obtained from human volunteers. A spectrum of antigens with a wide range of molecular weights (14 to 126 kilodaltons) were identified by antibodies in human serum for each species. Both species-unique and species-shared antigens were present. The results of these studies indicate that the humoral response to mosquito bite is complex, with a multitude of antigens provoking antibody responses. Since each individual has his or her own unique exposure history to mosquitoes, it seems unlikely that desensitization to a specific immunogen will confer protection in clinical situations in which multiple exposures to a variety of mosquito species occur.