Summary The large intestine plays an important role in the salvage of electrolytes and water, although little is known of its function in early childhood in health or in disease. Using an in vitro voltage clamp technique, we have measured bidirectional sodium (Na) and chloride (C***l) fluxes (J), electrical potential difference (PD), short circuit current (Isc), and tissue resistance (R) in 10 pairs of healthy human infant left colon and four pairs of inflamed colon. In healthy tissue there was net Na and C***l absorption with JNa net approximating Isc. In contrast, inflamed colon exhibited significant reductions in PD, Isc, and R and increases in net serosa to mucosa flux of Na and Cl (JNasm and JClsm) resulting in net Na and Cl secretion. These results suggest that Na and Cl absorption in left colon is highly efficient in young children and that mucosal inflammation may seriously impair the colon's ability to conserve salt and water.