Gastric acid secretion and gastric emptying rate was measured using double marker method and continuous titration of a liquid peptone test meal. Titration rate was significantly reduced by 30 ml of an aluminiumhydroxide- and magnesiumhydroxide containing antacid compound (Maalox). Acidity of gastric contents was reduced over a period of 48.4 +/- 9.1 min (mean +/- SD; endpoint of titration pH 5.5) and 77.6 +/- 2.0 min (pH 3.5) (p less than 0.05). The histamine H2-receptor blocker Ranitidine (0.25 mg/kg b.w.) and the antimuscarinic agent Pirenzepine reduced titrable gastric acid secretion in a similar range, as far as the observation period of 90 min is concerned. Biosorbin MCT, a formula diet, stimulated gastric acid secretion half the amount of gastric acid secretion stimulated by the peptone meal. Gastric emptying rate was significantly reduced by formula diet, but not by either of the other compounds.