The effects of bivalent cations, pH, anions, 2,4-dinitrophenol, dicyclohexylcarbodiimide and roseofungine on the anion-sensitive ATPase from rat liver plasma membranes were studied. It was found that ATPase from plasma membranes is similar to the anion-sensitive ATPase of rat liver nuclei and differs in some features from mitochondrial ATPase.