CEA, SCC and CYFRA 21-1 were measured in samples of serum coming from 105 'Non small cell lung cancer' (NSCLC) patients. The present study has been carried out to compare these markers, to analyse their prognostic significance and to determine the best combination of tumor markers. The median value and interquartile range were: CYFRA 21-1: 2,3 ng/ml, CEA: 3,7 ng/ml, SCC: 1,2 ng/ml. CEA demonstrated higher values in adenocarcinomas (P = 0.04). SCC and CYFRA 21-1 were comparable in the different histologic groups. CYFRA 21-1 and CEA values were dependant on tumor stage. Advanced tumors (T3 and T4) demonstrated higher serum CYFRA 21-1 level (P = 0.0006). CYFRA 21-1 was higher than 3,3 ng/ml in 36% of patients. CEA was higher than 5 ng/ml in 38% of patients and SCC was higher than 2 ng/ml in 27% of patients. Patients with a high CEA and CYFRA21-1 serum level had a shorter survival than those with a normal serum level. In a Cox regression analysis four variables (TNM stage, age, CYFRA 21-1 and CEA level) were found to be significant in the prediction of survival; CYFRA 21-1 level had the lowest P value (P = 0.0002). The current study suggests the use of a combination of CEA and CYFRA 21-1 in the clinical care of NSCLC.