To gain a better understanding of molecular changes in oral squamous cell carcinomas, we tested fresh tumour specimens from 110 patients for erbB-1 and -2 oncogene aberrations using the competitive differential polymerase chain reaction. The significance of established tumour characteristics such as TNM stage, differentiation and oncogene aberrations for tumour progression were analyzed. ErbB-2 amplification with a gene copy number > 1.6 in tumour tissue and erbB-1 deletion with a gene copy number < 0.4 in tumour-surrounding mucosa are of clinical relevance and indicate an early tumour recurrence or metastasis (p < 0.05). In T1/T2 tumours an erbB-2 gene dosage study allows differentiation between tumours with high or low risk for early progression. In a multivariate statistical analysis T stage (p < 0.01) and erbB-2 amplification in tumour material (p < 0.05) were independent prognostic variables.