agricultrual chemical transport modeling requires predicting insecticide washoff by rainfall from plant canopy to soil and its subsequent transport in runoff and sediments. one such chemical, toxaphene (chlorinated camphene), is applied to cotton for insect control in the south during july and august, months of high-intensity thunderstorms. toxaphene washoff from mature cotton was measured using a multiple-intensity rainfall simulator. toxaphene washoff per unit of rain was independent of rainfall intensity when 2. 4 cm simulated rain was applied at 1. 3, 2. 5, 5. 1, and 10. 2 cm/hr 2 hrs after toxaphene was applied at 2. 24 kg/ha. only 1. 3% of the applied toxaphene was washed off the cotton plants. only rainfall amount affected toxaphene washoff. toxaphene concentrations in the washoff decreased with time as power functions with exponents between $minus$ 0. 52 and $minus$ 0. 68 this information greatly simplifies modeling the movement of toxaphene from plant canopy to soil during natural rainfall events when intensities vary greatly within events and from storm to storm. refs