In the present study it was the aim to examine the effect of a postprandial plasma amino acid pattern on gastric acid secretion in man. Firstly, a new amino acid mixture of 18 amino acids was administered intravenously (10 g/h) to 8 normal subjects and the plasma amino acid levels correlated well with those observed after ingestion of a protein-rich meal (r = 0.91; p < 0.001). The i.v. administration of this solution elicited a small though significant augmentation of basal acid secretion (3.1 mmol/h) compared to controls while pentagastrin-stimulated (50 ng/kg/h) gastric acid secretion remained unaffected. In addition, plasma gastrin levels remained unchanged in the basal state during i.v. infusion of the amino acid solution. These results indicate that elevations of circulating plasma amino acid levels similar to those after ingestion of a protein-rich meal have--if at all--only a small stimulatory effect on basal acid secretion. Since plasma amino acids increase when gastric acid secretion has already been activated by cephalic or gastric phase mechanisms, their physiological relevance for the regulation of gastric acid secretion is negligible.