Ten healthy volunteers took part in a double-blind, randomized, cross-over study of the effect of single doses of enprostil (70 micrograms) and placebo on basal and meal-stimulated gastric acid, pepsin secretion and serum gastrin. Meal-stimulation was induced by modified sham feeding combined with repeated gastric instillation and withdrawal of meat soup. When studied between 1 and 2.5 hours after oral administration of the drug, enprostil decreased basal acid output by 92% (P less than 0.001) and stimulated acid output by 70% (P less than 0.001). Basal and stimulated volumes of gastric juice were decreased by 50% (P less than 0.02) and 35% (P less than 0.002), respectively. Enprostil decreased stimulated pepsin output by 34% (P less than 0.05), but had no effect on the concentration of pepsin. Neither basal nor stimulated serum gastrin concentrations were affected by enprostil. Percent recovery of the meal was measured by an unabsorbable marker, polyethylene glycol, instilled into the stomach mixed with the soup. Polyethylene glycol recovery decreased from 89% with placebo to 67% with enprostil (P less than 0.01), indicating an enhanced gastric emptying rate with enprostil.