The toxicities of methanol extracts from 28 medicinal plant species to early 4th instar larvae of Aedes aegypti, Ochlerotatus togoi (Aedes togoi), and Culex pipiens pal/ens were determined in the laboratory. Responses varied according to plant and mosquito species. At a concentration of 100 ppm, ＞90% mortality of the three species was obtained with the extracts of Cinnamomum cassia bark, Illicium verum fruit, Piper nigrum fruit, Zanthoxylum piperitum fruit, and Kaempferia galanga rhizome. P. nigrum fruit extract gave 100% mortality of larvae of Ae. aegypti and O. togoi at 5 ppm and 96% mortality of larvae of C. pipiens pallens at 2.5 ppm. Z. piperitum fruit extract gave 85, 100, and 48% mortality in larvae of Ae. aegypti, O. togoi, and Cx. pipiens pallens at 10 ppm, respectively. The plants described merit further study as potential mosquito larval control agents.