Purpose: The relationship was studied between c-erbB-2 expression and outcome in 107 carcinomas of the cervix treated with radical radiotherapy. Methods: Formalin-fixed, paraffin-embedded sections were stained by immunohistochemistry for over-expression of the c-erbB-2 protein. A retrospective study of treatment outcome was made on patients with a median follow-up of 55 months. Results: Patients with c-erbB-2-positive tumours had a significantly worse overall survival rate than those with c-erbB-2-negative tumours (P = 0.019). Metastasis-free survival (i.e. recurrence outside the radiotherapy field) was also significantly worse (P <0.001) but there were no differences in local control (i.e. recurrence within the radiotherapy field) rates (P = 0.24). Bivariate log-rank analyses showed that the prognostic value of c-erbB-2 expression for metastasis-free survival was independent of disease stage, histological grade, patient age, tumour size and tumour radiosensitivity. A combination of two biological parameters yielded a high discrimination between outcome groups. Women with radiosensitive and c-erbB-2-negative tumours had a 5-year metastasis-free survival level of 70% compared to 33% for women with radioresistant, c-erbB- 2-positive tumours. Conclusions: c-erbB-2 expression is an important prognostic factor for determining tumour recurrence outside the treatment field in cervix carcinomas treated with radiotherapy.