Larvicidal activity of methanol extracts of 22 Australian and 12 Mexican plants against early 4th-instar larvae of Aedes aegypti and Culex Pipiens pallens was examined. At 200 ppm, 100% mortality in larvae of A. aegypti and C, pipiens pallens was obtained in extracts of Kigelia pinnata and Ruta chalepensis. The extract off. pinnate gave 76.3 and 80.3% mortalities in larvae of A. aegypti and C. pipiens pallens at 100 ppm but, at 50 ppm, 23.7 and 42.1% mortality against larvae of 1. aegypti and C. pipiens pallens, respectively. The extract of R. chalepensis gave 81.2 and 87.9% mortality in larvae of .A. aegypti and C. pipiens pallens at 100 ppm but 23.4 and 53,3% mortality against larvae of 1. aegypti and C. pipiem pallem at 50 ppm, respectively. Larvicidal activities of K. pinnata and R. chalepensis extracts were significantly reduced when used at 25 ppm. Consequently, further studies of these plants as possible agents for mosquito control are warranted.