The aim of this study was answering the question whether cytofluorimetric determining of DNA ploidy, p53 and bcl-2 expression in tumour cells may enhance the diagnosis of squamous epithelial lung carcinoma. Samples of neoplastic tissue were taken from 11 operated patients. DNA staining was performed with propidium iodide. p53 and bcl-2 expression was evaluated by using monoclonal antibodies. By assessing of DNA ploidy we observed increased proliferative activity and, at the same time, high rate of the cell necrosis. In the analysis of p53 protein the presence of antigen was observed on average in 7.1 +/- 2.4, 15.1 +/- 3.9, and 19.8 +/- 4.1% of normal cells of the pulmonary tissue, the peripheral part of the tumour and cells of the central part of the tumour, respectively. bcl-2 was found on average in 7.3 +/- 2.2, 9.9 +/- 3.1, and 12.4 +/- 3.19% of the above cells, respectively. These results show that the technique of cytofluorimetric evaluation of p53 and bcl-2 proteins can be useful in diagnosis of pulmonary cancer in addition to classic histological and immunohistochemical methods.