To test the hypothesis that plasminogen activator inhibitor-1 (PAI-1) may serve as a candidate marker for the malignancy of colorectal cancer (CRC), we performed a quantitative RT-PCR for PAI-1 gene and evaluated the possible relationship between PAI-1 gene expression levels and clinicopathological findings in CRC. A significant increase in PAI-1 expression scores was observed in lymph node metastasis-positive CRCs (2.19 +/- 0.43) compared to negative ones (0.35 +/- 0.42) (P = 0.0037) as well as in distant metastasis-positive CRCs (3.50 +/- 1.18) compared to negative ones (0.99 +/- 0.30). The PAI-1 expression score markedly increased with the tumour stage (P = 0.0063; ANOVA test). Moreover, multivariate analysis revealed the PAI-1 expression score to be a strong and independent prognostic factor for CRC (P = 0.0432). These results suggested that PAI-1 might serve as a new parameter for the prediction of prognoses in CRC.