In order to determine whether tadpoles of Hyla septentrionalis are effective predators of larval peridomestic mosquitoes, larvae were exposed to tadpoles and the association between larvae and tadpoles in nature was recorded. Tadpoles were cannibalistic, eating egg masses of their own species, as well as a variety of material of both plant and animal origin. Tadpoles captured and ate more than 13 larval Culex pipiens per day. In natural breeding sites on Grand Bahama Island, larval C. pipiens were never abundant in sites that contained tadpoles and when tadpoles were introduced into vessels that contained mosquitoes, these containers soon became free of mosquitoes. The habitat of H. septentrionalis tadpoles in the study area seemed identical to that of larval C. pipiens and more than half of apparently suitable sites contained tadpoles. Thus, the presence of these frogs appeared to limit the abundance of C. pipiens.