It was shown by immunohistochemical methods, using antisera against highly purified carbonic anhydrases CA I, II and III, that CA II and CA III are specifically located in hepatocytes around central veins of adult rat livers. CA II was found in these perivenous hepatocytes of both male and female rats. Its physiological role is probably to facilitate the secretion of bicarbonate ions by these cells into canalicular bile. CA III and CA I were found in the same hepatocytes but only in the livers of male rats. The function of CA I and CA II exclusively in these cells of male rats cannot be simply explained.