A high prevalence of duodenal ulcer has been reported in patients with chronic pancreatitis. Data from previous studies on gastric acid secretion in these patients have provided conflicting results, and the potential role of H. pylori infection has been poorly investigated. The aim of this study was to assess the circadian pattern of gastric acidity and the prevalence of H. pylori infection in a group of patients suffering from this disease. Thirty-five patients with chronic pancreatitis ascertained by means of pancreatic calcifications or ductal alterations revealed by ERCP were recruited for this prospective study. They underwent 24-hr gastric pH-metry with glass minielectrodes positioned in the gastric corpus, and their profile of gastric acidity was compared with that of 35 healthy subjects, matched for age and sex. H. pylori infection was diagnosed by means of serology. There was no statistical difference (P = NS) in gastric pH of circadian, nocturnal, daytime, and postprandial periods between healthy subjects and patients with chronic pancreatitis. The prevalence of H. pylori infection was rather low (31%) in our patients and similar to that of a comparable control population (37%) in our geographical area. In conclusion, our study shows that patients with chronic pancreatitis have a circadian pattern of gastric acidity similar to that of normal subjects. Moreover, the prevalence of H. pylori infection is low in this population. These findings greatly differentiate the ulcer diathesis in chronic pancreatitis from that of patients with ordinary duodenal ulcer and suggest that other factors are implicated in the ulcerogenic process.