The epidermal growth factor receptor (EGFR) is structurally similar to the c-erbB-2 oncogene protein. One hundred and nineteen specimens of primary human lung adenocarcinoma were investigated immunohistochemically for the expression of EGFR and the c-erbB-2 protein. Positive staining for EGFR was evident in 55 (46%), and c-erbB-2 protein in 33 (28%) cases. Of the 119 cases, the number staining positively for both the EGFR and c-erbB-2 protein totalled 16 (13%). The incidence of both the expression of EGFR and the c-erbB-2 protein was greater in patients with metastasis1 (M1) than in those with M0 (P < 0.01). The 5-year survival rates of patients with EGFR positivity and those with EGFR negativity were 51% and 42% respectively, however, the results did not show statistical significance. On the other hand, the 5-year survival rates of patients with c-erbB-2 positivity and c-erbB-2 negativity were 30% and 52%, respectively, with statistical significance (P < 0.05). Of the cases with EGFR positivity the 5-year survival rates of patients with c-erbB-2 positivity (n = 16) and negativity (n = 39) were 33% and 59%, respectively, with statistical significance (P < 0.05). In contrast, for the EGFR negative cases, the 5-year survival rates of patients who were positive (n = 17) and negative (n = 47) for c-erbB-2 expression were 27% and 46%, respectively, which were not significantly different. Our data thus suggested that erbB oncogenes may play an important role in both the development of cancer and the prognosis of adenocarcinoma of the lung.