The effect of various detergents treatment on the specific binding of [3H]PK 11195 (2nM) to peripheral-type benzodiazepine binding sites (PBS) in calf and rat kidney, adrenal gland, and cerebral cortex membranes was studied. At a concentration of 0.025%, Triton X-100 increased [3H]PK 11195 specific binding to calf kidney, adrenal gland, and cerebral cortex membranes by 20-40%. At the same concentration, Triton X-100 scarcely affected specific binding of [3H]PK 11195 to rat cerebral cortex but decreased binding to rat kidney and adrenal gland membranes by 20-30%. At a concentration of 0.05% of Triton X-100, [3H]PK 11195 specific binding to calf kidney, adrenal gland, and cerebral cortex membranes was increased by 10-20%; whereas [3H]PK 11195 specific binding to rat kidney, adrenal gland, and cerebral cortex membranes was decreased by more than 40%. The increase in [3H]PK 11195 specific binding to calf kidney membranes following Triton X-100 (0.05%) treatment was apparently due to an increase in the binding affinity of PBS, since the density remained unaltered; whereas, the decrease in [3H]PK 11195 specific binding to rat kidney membranes was due to a decrease in both binding affinity and density of PBS. On the other hand, the detergents 3- [(3- cholamidopropyl)- dimethylammonio] - 1 - propane sulfonate (CHAPS), Tween 20, deoxycholic acid, and digitonin have a similar effect on [3H]PK 11195 specific binding to PBS in both calf and rat kidney membranes.