During malignant growth many changes take place in the metabolism of fibrillar type III collagens in the connective tissues. The aminoterminal propeptide of type III procollagen (PIIINP) has been found to be often elevated in ovarian cancer. In the present study the prognostic value of serum PIIINP concentration in epithelial ovarian cancer is evaluated in relation to serum CA125. Fifty-six women were enrolled in the study. Serial venous blood samples were taken preoperatively and 6, 9 and 12 months after operation for PIIINP and CA125 determinations. The results were correlated to the three-year survival. In Kaplan-Meier survival analysis the preoperative (P = 0.0422), 9-month (P = 0.0062) and 12-month (P = 0.0062) serum PIIINP concentration distinguished between the patients with good and poor prognosis while CA125 did so only at 9- (P = 0.0005) and 12-month (P