The c-erbB-2 proto-oncogene encodes a growth factor receptor which is over-expressed in a variety of human adenocarcinomas. Recent reports suggest that it may be of value in arriving at prognosis in breast and ovarian cancer. In this study, c-erbB-2 expression was investigated in 93 routinely processed cases of gastric carcinoma, using an immunohistochemical technique. c-erbB-2 membrane immunoreactivity was observed in 11% (10/93) of tumours, all of which were of the well differentiated intestinal type (p less than 0.01). Overall, patients with tumours expressing this proto-oncogene had a significantly improved prognosis (p less than 0.05). Within the group of intestinal-type tumours, those that were c-erbB-2-positive formed a distinct sub-population which had a better prognosis (p less than 0.02), suggesting possible differences in aetiology.