Numerous studies have shown that alcohol causes both acute and chronic damage to gastroduodenal mucosa. The methods of damage differ however, and experimental studies in animals have shown that the degranulation of mast cells in gastric mucosa causes acute hemorrhagic lesions after the consumption of alcohol. It is not known whether this mechanism also operates in man. The aim of the present study was therefore to evaluate whether there is a correlation between mast-cell activation, determined by assaying tryptase levels in gastric mucosa, and the consumption of alcohol in patients with ulcerative diseases. Thirty-one patients with cicatrized ulcerative lesions (13 gastric ulcers, 18 duodenal ulcers) were included in the study. Biopsies at the level of the gastric fundus and antrum and the duodenal bulb were performed in all patients to determine tryptase levels. Biopsy material was frozen and subsequently homogenized; the enzyme was assayed in the supernatant using a radioimmunometric method. The mean daily alcohol consumption was calculated in clinical terms for each patient over the past 5 years and patients were subdivided into non-drinkers and moderate ( 60 g alcohol/day) drinkers. It was found that tryptase concentrations were higher in the fundus compared to the gastric antrum and duodenal bulb, irrespective of alcohol consumption both in patients with gastric ulcer and duodenal ulcer. The importance of mast cells in provoking alcohol-dependent damage was studied at a gastric level. Alcohol leads to their degranulation and therefore contributes to the formation of gastric lesions.(ABSTRACT TRUNCATED AT 250 WORDS)