Duodenogastric reflux of bile and pancreatic secretions is known to induce acute chronic alterations of gastric and oesophageal mucosa. Several complex methods have been reported to demonstrate duodenogastric reflux (DGR) in man. The aim of this work was to describe a simple test for evaluation of DGR. The studied groups included: 1) 30 patients with DGR demonstrated by the radiological test of Capper and by endoscopic examination (group I); 2) 18 subjects without demonstrable DGR (group II). Bilirubin concentrations were measured in gastric juice collected for 10 min periods during one hour before and one hour after gallbladder stimulation by cholecystokinin-pancreozymin (CCK-PZ) (35 Ivy-dog Units). Bilirubin output was determined in the basal state (basal bilirubin output); maximal bilirubin peak (MBP) was determined by the highest of the collected samples following CCK-PZ administration. There was no significant difference between the two groups for basal bilirubin output. Analysis of the MBP showed that the two groups were significantly different (p less than 0.05). A duodenogastric reflux is present and can be quantitated when the MBP is above 200 microgram. Our results suggest that this method is available to evaluate the role of duodenogastric influx in gastric and/or oesophageal diseases.