Patients (n = 72) with newly diagnosed non-mucinous ovarian carcinomas, FIGO stages IIC-IV, and CA 125 levels raised when starting chemotherapy were followed both by serial serum CA 125 tumor marker determinations during induction chemotherapy and by second-look operation after 4-6 cycles of chemotherapy. Patients with complete response at the second-look operation (n = 19) had an estimated survival of 75% 59 months after the operation, compared with 22% in the 53 patients with persisting disease (p = 0.0004). Patients (n = 23) with a serum CA 125 half-life shorter than 16 days during induction chemotherapy had an estimated survival of 68% 59 months after the second-look operation as compared with 18% in 49 patients with a CA 125 half-life of more than 16 days (p = 0.003). Thus both second-look operation and serial CA 125 measurements fairly accurately predicted the patient survival, although the groups of patients identified by the two methods differed slightly. There was a strong correlation between the second-look results and the residual tumor after the primary operation. Interestingly, this association could not be found for tumor marker pattern, which could mean that this is an independent prognostic factor.