The effects of posture on gastric emptying, intragastric distribution, and antropyloroduodenal motility after ingestion of a nonnutrient liquid have been evaluated. In seven healthy volunteers antropyloroduodenal pressures were measured for 30 min after ingestion of 150 ml of normal saline in two different positions: sitting and left lateral. Saline drinks were radiolabeled and ingested both before and after intravenous atropine (4 micrograms/kg). Rates of emptying from both the total (P < 0.05) and the proximal (P < 0.05) stomach were faster in the sitting position than in the left lateral position. There were more long (> 6 cm) antropyloric pressure waves (P < 0.05) and isolated pyloric pressure waves (P < 0.05) in the sitting position. Intravenous atropine slowed emptying in both positions (P < 0.05) and in the sitting position decreased (P < 0.05) the number of antropyloric pressure waves. After atropine, gastric emptying was also faster in the sitting compared with the decubitus position (P < 0.05), although there was no difference in antropyloric or isolated pyloric pressure waves between the two postures. We conclude that the effects of gravity on gastric emptying of nonnutrient liquids are likely to reflect changes in both antropyloric motility and intragastric distribution.