The prognostic value of the tumor markers CYFRA 21-1, tissue polypeptide specific antigen (TPS) and carcinoembryonic antigen (CEA) was investigated in three histologic subtypes of non-small cell lung cancer. Pretreatment serum marker levels were measured in 38 patients with adenocarcinoma (AC), in 43 patients with squamous cell carcinoma (SQC) and in 35 patients with large cell carcinoma (LCC). Univariate analysis in AC showed significant lower survival of patients with elevated levels of TPS, CYFRA 21-1 and CEA. In LCC, elevated levels of TPS and CEA were found to predict lower survival, while in SQC--only TPS was a predictor. A multivariate analysis of survival identified CEA (Relative Risk-5.5; p = 0.004), CYFRA 21-1 (RR-3.4; p = 0.008) and TPS (RR-3.0; p = 0.02) as independent prognostic factors in AC. In SQC, only TPS (RR-2.3; p = 0.03) was such a factor whereas in LC--none of the markers studied retained statistical significance. Thereafter, the combinations of the two strongest prognostic factors in the AC group--CEA and CYFRA 21-1 were explored to divide this group into subsets with different prognosis. In cases where both markers were positive, the relative risk of death was 10.5 times higher as compared to cases where both markers were negative (p = 0.002).