The effects of three electrolyte transport inhibitors on the secretory and absorptive function of the human eccrine sweat gland were examined. Amiloride and furosemide at 10(-4) mol/l had no detectable effect on secretion while ouabain at 10(-4) mol/l completely inhibited secretion. In contrast, when amiloride, ouabain and furosemide were applied at 10(-4) mol/l to the luminal surface of the sweat duct by microperfusion, only amiloride blocked Na reabsorption. When the same inhibitors were added to the bathing solution at the same concentration, only ouabain inhibited Na reabsorption detectably. Present findings suggest that the secretory epithelium is permeable to solute and water movement while the duct epithelium is probably impermeable with respect to fluid movement across it.