In infants, adequate colonic function is vital in preventing electrolyte and water depletion. In certain species, short-chain fatty acids have been shown to increase colonic Na absorption. Using an in vitro voltage-clamp technique, we have studied the characteristics of electrolyte transport in isolated preparations of human left-sided colonic mucosa and investigated the effect of acetate on epithelial Na movement. In the basal state, there was net Na absorption that was entirely electrogenic. The addition of mucosal acetate resulted in a significant increase in net Na absorption that was markedly inhibited by amiloride, suggesting that, in the young child, the presence of shortchain fatty acids promotes colonic salvage of Na and that such salvage of Na may be via an amiloride-sensitive Na channel and involve stimulation of sodium-hydrogen exchange.