DNA flow cytometry;was used to study ploidy and cell cycle phase in patients with non - small cell lung carcinoma. A total number of 80 tumor samples were investigated. Cell cycle analysys was possible in 42 tumors. 79% of the tumors were aneuploid and 21% had diploid tumors. There was a correlation between high S-phase fraction in aneuploid tumors and lower S-phase fraction in diploid tumors. Patients with a lower S-phase fraction had a tendency to better survival, both diploid and aneuploid tumors.