Immunohistochemical study of epidermal growth factor (EGF), epidermal growth factor receptor (EGFR) and transforming growth factor-alpha (TGF-alpha) expression was performed on paraffin-embedded tissue specimens of 70 squamous cell lung carcinomas. The carcinomas were placed to one of the following eight groups, according to the results of EGF, TGF-alpha and EGFR expression: group 1: none, group 2: only EGFR, group 3: EGFR and TGF-alpha, group 4: EGFR and EGF, group 5: TGF-alpha and EGF, group 6: all three, group 7: only TGF-alpha and finally group 8: only EGF. Statistical analysis of the results revealed that the ratio of squamous cell lung carcinomas with lymph node metastasis was significantly higher in groups 4, 5 and 6 (P less than 0.01). We also examined whether EGF receptors were truncated with the use of two monoclonal antibodies directed against different portions of the receptor (EGFR1 and F4). No truncated EGF receptors were detected. These results suggest that lung carcinomas expressing the molecules EGF/EGFR, TFG-alpha/EGFR or TGF/alpha/EGF/EGFR display pathologic features of more aggressive disease.