The presence of pS2 protein (pS2) was studied in a total of 120 consecutive patients with gastric carcinomas. This immunohistochemical study found pS2 expression in 48 per cent (n = 58) of carcinomas. pS2 expression was also detected in normal gastric mucosa in 95 per cent (n = 102) of specimens in upper antral mucopeptic glands and deep foveolar cells of the gastric pits but not in intestinal metaplasia. There was a significant statistical correlation between pS2 expression and extent of tumour growth (pT state) and expression of pepsinogen II by the tumours. There was no statistical correlation with clinical features such as patient age or sex or other pathological parameters (tumour stage, size, grade, and localization or growth pattern according to histological classification). There were no statistically significant differences in survival times between patients with pS2-positive and pS2-negative tumours. In contrast to findings concerning breast cancer, pS2 expression in gastric carcinomas had no influence on the patient's prognosis. On the other hand, strong expression of pS2 by surface epithelium of normal gastric mucosa may indicate that pS2 might play a role in physiological cell renewal of normal gastric mucosa.