Pretreatment sera of 78 patients with squamous cell cervical cancer were tested for the presence of cytokeratin 19 (CK 19) fragments to determine the relationship among this parameter, tumor stage, various histopathologic characteristics, and prognosis. For the quantitative determination of CK 19 fragments in serum, the enzyme assay Cyfra 21-1 was used. This assay, based on the simultaneous sandwich principle, utilizes two different monoclonal antibodies. The test was considered positive when levels of Cyfra 21-1 were > or = 1.2 micrograms/liter. Cyfra 21-1 was positive in the majority of patients and in all patients with advanced disease (FIGO III or IVa). A highly significant relationship was found between pretreatment Cyfra 21-1 level and FIGO stage (P < 0.0001). Mean Cyfra 21-1 concentration was elevated in the case of macroinvasive disease (FIGO Ib, IIa, IIb, III, IVa). A distinct relationship was found between tumor size (P < 0.001; r = 0.73) and Cyfra 21-1 level. In the univariate Cox analysis Cyfra 21-1 level was significantly related to both disease-free interval (P < 0.0001) and survival (P < 0.0001) of patients. Patients with an increased Cyfra 21-1 level had a significantly worse prognosis. However, in the stepwise Cox regression analysis, these variables had no additional value over known prognostic factors such as FIGO stage and tumor size. It is concluded that Cyfra 21-1 may be of significance as an additional marker in the management of patients with cervical cancer, but further investigation is needed.