Chlordecone (Kepone) is a close structural analog of mirex, but it differs considerably from mirex in toxic action. Chiordecone primarily produces neurotoxic symptoms such as tremors in humans and animals. As with other organochlorine pesticides, the mechanism of the toxic action of chiordecone is not completely understood. An attempt is made in this paper to review the effects of chiordecone on the membrane‐bound adenosinetriphosphatases (ATPases) and related phenomena. Chiordecone is shown to be a potent inhibitor of A TPases in different tissue preparations of several species. The order of sensitivity of the ATPases tested to chiordecone was: oligomycin‐sensitive (mitochondrial) Mg2+‐A TPase > Na+, K+‐ATPase > Ca2+‐ATPase > oligomycin‐insensitive Mg2+‐ATPase. Compared to other tissues tested, brain Na+K+‐ATPase and heart mitochondrial Mg2+‐A TPase were more sensitive to chiordecone. Oligomycin‐insensitive Mg2+‐A TPase was the least affected enzyme.