The effects of different pharmacological agents and incubation media on the intracellular pH and water content of Amphiuma erythrocytes were investigated in vitro. Adrenaline had no significant effect on the intracellular pH or cell water content. DIDS caused an intracellular alkalinization that could be abolished by amiloride, ouabain or removal of sodium from the incubation medium. In addition, amiloride and DIDS both caused a decrease in cell water content. The data indicate that sodium/proton and chloride/bicarbonate exchangers are present on the membrane of Amphiuma erythrocytes and these exchangers are active under steady-state conditions.