The acute effects of ethanol on gastrointestinal transit were studied in mice. Intraperitoneal injection of 2 or 3 g of ethanol/kg had a dose-dependent inhibitory effect on gastrointestinal transit. Subcutaneous injection of 4 g of ethanol/kg also inhibited gastrointestinal transit, but this route was less effective than the intraperitoneal route of administration. Further examination of both the time course of inhibition and the weight of the stomach contents suggested that intraperitoneal injections of moderate doses of ethanol did not alter gastric emptying. The data indicated that gastrointestinal transit is inhibited by ethanol and that the most sensitive locus is the small intestine rather than the stomach.