Three insecticides (chlorpyrifos, parathion, and carbofuran) and 2 herbicides (propanil and molinate) were tested in laboratory and field to determine their toxicity against mosquitofish,Gambusia affinis(Baird&Girard), and green sunfish,Lepomis cyanellusRafinesque. In laboratory tests, green sunfish were more susceptible than mosquitofish to all pesticides tested except molinate. Parathion and chlorpyrifos were the most toxic compounds to green sunfish with comparable LC50'S. The most toxic compound to mosquitofish was parathion. Carbofuran was the least toxic insecticide to both species. Propanil was substantially more toxic than molinate which was the least toxic pesticide tested. In almost all instances the greatest mortality was observed between 24 and 48 h with very slight changes generally occurring between 48 and 72 h.All pesticides with the exception of parathion at 72 hand chlorpyrifos at 24, 48, and 72 h killed less than 10.0% of all fish tested when applied at recommended field dosages. Parathion produced 16.7% mortality to mosquitofish in cage tests 72 h posttreatment. Mortality from chlorpyrifos was 74.4% at all observation intervals against green sunfish in free-release studies. Propanil applied as much as 6-fold the recommended field dosage against green sunfish resulted in no mortality.