The study was designed to explore the tumour cell expression of three markers: hCG, SP1 and CEA in lung cancer in relationship with histological type and histological differentiation of tumours as well as serum concentration of antigens. 58 primary resected lung cancers: 28 adenocarcinomas, 27 squamous cell and 3 large cell carcinomas were included. Tumours immunoreactivity of three markers was evaluated by semiquantitative analysis. Simultaneously serum tumour markers were measured in 42 patients by enzyme radioimmunoassays. CEA and SP1 expressions in lung tumours were found in a majority of carcinomas-86% and 79% respectively. Expression of tumour markers was not associated with any certain histological type of carcinoma but was more characteristic for moderately and well differentiated adenocarcinomas. hCG positive tumour staining was less frequent than CEA and SP1 (only 22% tumours) and was much less intensive (5-50% population of carcinomatous cells) in the tumours. The study showed correlation between increased serum CEA concentration and tumour expression of antigen.