The current state-of-the-art for measuring or estimating pesticide retention and transformation parameters required in nonpoint source pollution models was reviewed. A data base of sorption partition coefficients, degradation rate coefficients, and half-lives for a broad spectrum of pesticides was compiled from a literature survey. Adsorption partition coefficients normalized with respect to soil organic carbon content were approximately constant across soils for a given pesticide. Octanol-water partition coefficients were good predictors of pesticide adsorption parameters. Chemical persistence in soils for a large number of pesticides has been measured under a variety of soil environmental conditions. These data were used to calculate first-order decay coefficients and half-lives. The variability of these degradation parameters for a given pesticide across several soils was within a factor of two. Multiple regression equations that correlated degradation (or disappearance) rates with soil properties could not be developed from the literature data because of inadequate information regarding soil physical, chemical, and environmental conditions during the pesticide degradation studies. Seasonal losses by runoff from agricultural fields were generally less than 0.5 - 1.0% of the total amount applied. Although pesticide concentrations on the sediment phase of the runoff are larger than those in the water phase, pesticide carried in the water phase accounted for more than 90% of the total mass emission during a given runoff event.