The expressions of epidermal growth factor (EGF) and its receptor were studied immunohistochemicafly in a total of 156 gastric carcinomas; 26 early and 130 advanced. No EGF immunoreactivity was found in early carcinomas, while EGFpositive tumor cells were detected in 38 (29.2%) of the 130 advanced carcinomas. EGF receptor immunoreactivity was detected in one (3.8%) of the 26 early carcinomas and in 44 (33.8%) of the 130 advanced carcinomas, the incidence being significantly different @<0.01). Out of the 130 advanced carcinomas, 17 (13. I %) had synchronous expression of EGF and its receptor and most of the tumors with strong expression of EGF were positive to EGF receptor. A significant correlation was observed between the depth of tumor invasion and EGF or its receptor immunoreactivity in tumor cells @< 0.05). Furthermore, a good correlation was demonstrated between the synchronous expression of EGF and i t s receptor and the depth of tumor invasion or the tumor staging. The incidence of cases with EGF in metastatic tumors was significantly higher than that in primary tumors @< 0.05). Patients with synchronous expression of EGF and i t s receptor had a far poorer prognosis than those without EGF and receptor.