The enhanced expression of thymidylate synthase (TS) has been associated with a poor prognosis in patients with several types of epithelial tumors. To determine the association between TS expression and the prognosis of patients with advanced cervical cancer after radiation therapy, we immunohistochemically assayed TS levels in paraffin-embedded tissue sections from 66 patients with stage IIIb cervical cancer using a polyclonal antibody to recombinant human TS. In the 30 patients with high TS expression, the cumulative 5- and 8-year survival rates were 36.8% (95% CI: 17. 4-56.2) and 31.6% (95% CI: 12.4-50.7), respectively. In contrast, the 36 patients with low TS expression showed a significantly (p < 0. 001) better prognosis, with cumulative 5- and 8-year survival rates of 87.2% (95% CI: 75.5-99.0) and 69.2% (95% CI: 50.7-87.7), respectively. These results suggest that TS expression may be useful in determining the prognosis of patients with advanced cervical cancer.