CD44 variants containing v6 confer metastatic potential to rat carcinoma cell-lines. In man, CD44v6 is increasingly expressed during colorectal tumour progression. In 68 colorectal carcinoma patients, survival analysis showed that CD44v6 expression in the tumours was associated with tumour-related death. In patients who had an apparently radical resection of their primary tumour, CD44v6 expression had prognostic value independent of Dukes' stage. CD44v6 expression may reflect propensity for metastasis after apparently curative surgery, making adjuvant therapy an option in these patients.