The mosquitofish, Gambusia affinis, and the inland silverside, Menidia beryllina, were evaluated in experimental, one-tenth hectare wild rice plots in Lake County, California, for their impact on densities of Culex tarsalis, Anopheles freeborni and Anopheles franciscanus. Gambusia affinis were tested at 0.6 and 1.7 kg/ha and the silversides at ca. 0.9 kg/ha. The silversides did not survive well in the rice field system and none of the silverside guts examined contained mosquito larvae. The mosquitofish increased steadily throughout the season and mosquito larvae were found in 9% of the fish dissected. Analysis of variance did not reveal significant differences among the mosquito populations in the 3 fish treatments and controls on any sampling date. More than 40 species of aquatic insects were collected and population densities of selected aquatic insects were similar among the 4 treatments.