The aims of the study were to assess the degree of ploidy and determine whether it had any influence on the remission time and survival of surgically treated patients with squamous cell lung cancer. The results were then related to the clinical staging, grading, size and location of the tumor. Tissue samples of squamous cell lung carcinoma (n=80) resected between 1995 and 1996 in the Department of Thoracic Surgery at University of Medical Sciences in Poznan were prepared using the modified Hedley's method. The measurements were made by means of a Cytoron Absolute flow cytometer. Abnormal (aneuploid) DNA was found in 45% of the tumors. In the 2-year observation period significantly more patients with aneuploid tumors died (75%) than those with diploid tumors (43.2%), P<0.05. No significant correlation was found between the ploidy and frequency of metastasis to regional lymph nodes, tumor size, location or grading. Estimation of the DNA content in cancer cells appears to be a significant prognostic factor. Furthermore measurement of the DNA content can be useful after surgery to estimate the risk of recurrence.