The KCl cotransporters KCC3 and KCC4 are expressed at the basolateral membrane of proximal convoluted tubule cells, and KCC4 is present in the basolateral membrane of the thick ascending loop of Henle's limb and the α-intercalated cells of the collecting duct. Little is known, however, about the physiological roles of these transporters in the kidney. We evaluated the KCC3 and KCC4 mRNA and protein expression levels and intrarenal distribution in male Wistar rats or C57 mice under five experimental conditions: hyperglycemia after a single dose of streptozotocin, a low salt diet, metabolic acidosis induced by ammonium chloride in drinking water, and low or high K+ diet. Both KCC3 mRNA and protein expression was increased during hyperglycemia in the renal cortex and at the basolateral membrane of proximal tubule cells but not a low salt diet or acidosis. In contrast, KCC4 protein expression was increased by a low sodium diet in whole kidney and by metabolic acidosis in the renal outer medulla, specifically at the basolateral membrane of α-intercalated cells. The increased protein expression of KCC4 by a low salt diet was also observed in WNK4 knockout mice, suggesting that up-regulation of KCC4 in these circumstances is not WNK4 dependent. No change in KCC3 or KCC4 protein expression was observed under low or high K+ diets. Our data are consistent with a role for KCC3 in the proximal tubule glucose reabsorption mechanism and for KCC4 in salt reabsorption of the TAL and acid secretion of the collecting duct.