The nm23 gene is a putative tumour and metastasis suppressor gene. A number of studies have found that reduction of its expression is associated with increased metastatic potential in several human malignancies. Similarly, clinical studies have shown correlation between reduced nm23 protein expression and a poor prognosis. The aim of this study was to determine if a relationship exists between nm23 expression in primary cutaneous melanomas with or without cerebral metastases. Paraffin-embedded tissues were retrieved from 21 patients with primary cutaneous melanomas (n=21) and who subsequently developed cerebral metastases (n=24). Primary cutaneous melanomas with no regional or organ metastases within a 10 year period were used as control cases (n=34). Nm23 staining was localized in the cytoplasm of the tumour cells. Most of the control cases showed strong expression, whereas the majority of the primary melanomas with cerebral metastases showed no or weak expression of nm23. The cerebral metastases mostly showed strong expression. In summary, the results of this study may have significant prognostic implications for patients presenting with cutaneous melanoma. Patients with cutaneous melanomas with a low expression of nm23 appear to be more at risk of developing brain metastases.