Studies of the Na+/H+ antiporter in epithelial cells have defined its basic properties, regulatory features, and responses to various activators and inhibitors. A special aspect in epithelial cells relates to the distribution of the Na+/H+ antiporter in the plasma membranes with respect to its specialized role in vectorial transport of protons across the epithelial cell barrier. The net effects of vectorial Na+/H+ exchange may include titration of extracellular buffer, cell volume regulation, as well as participation in the absorptive flux of Na. In general, the basic properties of the Na+/H+ antiporter are similar in a variety of epithelial tissues. 1 – 4 The best-characterized preparation is the brush border membrane vesicle from the renal cortex.