ABSTRACT MODELING pesticide transport in surface runoff or to groundwater from agricultural lands requires the ability to predict pesticide amounts washed from plants to the soil by rain. A multiple-intensity rainfall simulator was used to determine the effects of rainfall intensity and amount on carbaryl concentrations and amounts washed from mature cotton (Gossypium hirsutum L.) plants. Two hours after carbaryl was applied as a wettable powder at 1.73 kg ha'S rain (25 mm) was applied at 6.6, 12.7, 25.7, 51.3, and 106.4 mm h-i. Although rainfall intensity did affect carbaryl concentrations and amounts washed off, rainfall amount had a greater effect. The rainfall intensity effect on carbaryl washoff was more pronounced than in earlier studies with emulsifiable concentrate formulations of organochlorine, organo-phosphorus, and pyrethroid insecticides. Carbaryl concentrations in plant washoff decreased rapidly during the early phases of washoff. About 63% of the carbaryl on the plants 2 h after application was washed off by 25 mm of rain; an additional 76 mm of rain removed an additional 35% of the carbaryl from the plants. Although statistically there was a rainfall intensity effect on the concentrations and amounts of carbaryl washed from plants, the intensity effect may be ignored for predictive models from a practical standpoint.