In a study on the effect of hexachlorocyclohexane (HCH) on soil transformations in flooded soils, 5 percent granules of HCH were added to three soils to provide final concentrations of 5 to 100 parts per million of active ingredient, and the soils were flooded. Addition of HCH even at the 5-ppm level led to a remarkable decrease in the formation of Fe2+and, to a lesser extent, soluble manganese and prevented the drop in redox potentials in all soils. These effects of HCH were well pronounced also in the presence of added rice straw (0.5 percent), although rice straw alone hastened soil reduction. The inhibitory effect of HCH on soil reduction lasted even after 50 days of flooding.