In this review we present immunolocalization studies using a monoclonal antibody raised against the 31-kD subunit of bovine H-ATPase, and indirect immunofluorescent staining. In the proximal tubules there is intense H-ATPase staining in the brush borders of S1 and S2, and linear subvillar invagination staining in S1, S2, and S3 segments. In the thick ascending limb of the loop of Henle there is a mild to moderate degree apical cytoplasmic vesicular staining in both medullary and cortical segments. In distal convoluted tubule the H-ATPase staining is more sharply delineated along the luminal plasma membrane. In the connecting tubule, the connecting tubule cells show mild to moderate staining of the luminal membrane and apical cytoplasmic vesicular staining, and the intercalated cells demonstrated prominent H-ATPase staining which is polarized to either apical or basolateral pole or distributed diffusely throughout the cell. In the cortical collecting duct the principal cells show minimal or no staining while the intercalated cells show very bright H-ATPase sustaining with six discernible subtypes based on polarization of the pump to apical or basolateral poles, and the degree of polarization (well polarized or poorly polarized). In the medullary collecting duct the principal cells show no staining and the intercalated cells show H-ATPase staining only in the apical pole. We also describe adaptive responses to different physiologic conditions, e.g. chronic acid or alkali loads (with or without colchicine), chronic respiratory acidosis, chronic desoxycorticosterone administration, remnant kidney, and chronic potassium depletion diet. Moreover, we demonstrated the immunocytochemical localization of the H-ATPase pump in the rabbit kidney as compared to the rat kidney.