The expression of the cell-cell adhesion molecule E-cadherin has previously been shown to be reduced in poorly differentiated squamous cell carcinoma of the head and neck and absent in nodal metastases. Twenty-eight patients with previously untreated squamous cell carcinoma of the head and neck, 22 of whom had nodal metastases at presentation, were investigated for E-cadherin expression using the monoclonal antibody 6F9, specific for human E-cadherin. Reduced expression was seen in the poorly differentiated primary tumours, compared with well differentiated tumours, but this trend was not statistically significant. E-cadherin expression was present at a reduced level in nodal metastases. It was also noted that, where both the primary tumour and corresponding nodal metastasis were investigated, E-cadherin expression was identical for both samples. The degree of E-cadherin expression did not correlate with survival. These data confirm a reduction in E-cadherin expression in poorly differentiated tumours. There was no correlation between E-cadherin expression and any of the host, tumour and treatment factors associated with malignancies of the head and neck region.