Isotonic glucose, saline, and acid-saline solutions were instilled into acute postvagotomy, pylorus-ligated rat stomachs for periods of 45 min. Calculated net fluxes showed similar secretion of Na, Cl-, and K with all 3 solutions. No entry of H occurred with glucose and saline solutions, and there was a net loss of H when acid-saline was instilled. Glucose solutions became hypertonic, saline remained isotonic, and acid-saline became hypotonic. Subcutaneous injection of histamine acid phosphate, 5 mg/100 g , in the presence of instilled isotonic solutions, stimulated secretion of HC1 and K but did not affect Na output. Histamine had no significant effect on the electrolytes of the spontaneously secreting pylorus-ligated stomach. Studies of K secretion suggest that changes in K concentration after histamine may be related to processes of gastric stimulation rather than to HCl formation.