The effects of organic mercury compounds on the biomembrane were studied with specific reference to the K(+) compartment and the following results were obtained. 1) PhMC, PhMA, and MMC had effects of decoupling action on the oxidative phosphorylation, and PCMB inhibited the ADP-stimulated respiration, and mercury chloride inhibited the respiration. 2) On the red blood cell and mitochondrial membrane, these organic mercury compounds induced the K(+) release in the order of HgCl(2) PhMC PhMA MMC PCMB. 4) It is suggested that the liophilic nature of organic mercury compounds plays an important role in the reaction of K(+) release.