Primary head and neck squamous cell carcinomas from 58 patients were analyzed for the presence of alterations in the K-ras, raf, and erb-B oncogenes. Analysis of 17 fresh tumor specimens using sequence analysis of target sequences amplified by the polymerase chain reaction showed no evidence of mutations in the K-ras oncogene. Thirty fresh tumor specimens were analyzed for the presence of raf gene activation using Southern blot analysis. Under these conditions, no mutations in the c-raf oncogene were detected. In this study, 6 (13%) of the 47 tumors studied displayed epidermal growth factor receptor (EGFR) gene amplification and/or gene rearrangement. Overexpression of the erb-B gene was observed in 18 (67%) of the 27 head and neck tumors studied. Those patients expressing high levels of EGFR or showing EGFR amplification had tumors that were clinically more advanced. These data suggest that amplification and over-expression of the EGFR gene may be a useful diagnostic and prognostic marker in head and neck squamous cell carcinomas.