Urokinase-type plasminogen activator (u-PA) is a serine protease involved in cancer metastasis. Using immunohistochemical methods, we examined the relation between u-PA and long-term survival in 70 patients with Dukes' B colorectal cancer. 8-year survival was 81% in patients whose tumours demonstrated low-grade epithelial u-PA staining and 43% in those with high-grade staining (log-rank test, p = 0.01). Survival was unrelated to stromal u-PA staining. These results suggest that u-PA may be useful in the identification of patients with non-metastatic colorectal cancer at risk of tumour recurrence.