The interaction of three pesticides and two herbicides with various clays was studied. The five compounds studied were endrin, dieldrin, aldrin, amiben, and diquat. Endrin decomposition was greater on clays saturated with Al than those saturated with Ca, indicating that endrin decomposition will be increased by acidity of clay or soil. Increasing relative humidity generally reduced adsorption and decomposition of endrin. Endrin decomposition may be increased in sediments or soils by drying them by frequent tillage in a dry season. Diquat cations were 68 to 100% replaced by K ions in soil clays. Some diquat may remain active in the presence of kaolinite and vermiculite. Sorption of the amiben anion was greatest for minerals with hydroxyl surfaces and least for 2:1 layer structured minerals. Greater leaching could occur in soils dominated by 2:1 type minerals. Sorption of the methyl ester of amiben was largely controlled by organic matter content regardless of clay minerals present. Many of the soils of the southeastern United States are acid and contain vermiculite and kaolinite as the major clay minerals. These soils may be effective in decomposing endrin, diquat, and other organic molecules. (WRSIC abstract)