The aim of the present study was to evaluate the clinical usefulness of the cytokeratin marker CYFRA 21-1 as a screening marker for ovarian cancer, as a predictive marker in patients with adnexal masses and as a prognostic marker in women suffering from ovarian cancer. In order to determine the specificity of the CYFRA 21-1 test, we have investigated CYFRA 21-1 serum levels in several benign conditions. This retrospective study comprises 37 patients suffering from ovarian cancer FIGO stages Ia-III. Sera from patients with benign ovarian cysts, endometriosis, pelvic inflammatory disease, inflammatory bowel disease and liver cirrhosis were evaluated in 90, 10, 38, 10 and 20 cases respectively. With a sensitivity of 41% and a specificity of 95%, CYFRA 21-1 was not suitable as a screening marker for ovarian cancer. Although CYFRA 21-1 was able to discriminate between ovarian cancer and benign adnexal tumours (univariate regression model, P = 0.0001), CYFRA 21-1 did not reveal additional information to CA 125 in a multivariate regression analysis (P = 0.06). CYFRA 21-1 serum levels were elevated in benign conditions such as liver cirrhosis, but not in endometriosis and inflammatory diseases. In ovarian cancer patients, elevated CYFRA 21-1 serum levels before therapy were associated with a poor overall and disease-free survival (log-rank test, P = 0.02 and log-rank test, P = 0.005 respectively). CYFRA 21-1, while obviously not suitable for screening or differential diagnosis of adnexal masses, could be useful as an additional prognostic factor in ovarian cancer patients.