Immunohistochemical studies were performed to investigate the prognostic significance of p53 protein expression in 46 patients with stage IIIB squamous cell carcinoma of the uterine cervix who were treated with radiation therapy alone. Tumor cells showed p53 protein expression in 29 of 46 patients. The 5-year overall actuarial and cause-specific survival rates for the patients with p53-positive tumor were 52.9 and 70.4%, respectively. The corresponding rates for the patients with p53-negative tumor were 58.2 and 69.0%, respectively. There was no significant difference of local control rates and of distant metastases rates between the two groups. In conclusion, no relationship was observed between radiation treatment outcome and the immunohistochemically detected p53 protein expression in the patients with stage IIIB squamous cell carcinoma of the uterine cervix.