To evaluate prognosis and therapeutic significance, tumor DNA content(ploidy) and proliferative activity(percentage of cells in S and G2/M portion) was determined by flow cytomentry paraffin-embedded samples obtained from 30 patients with small cell lung cancer. Forty-six percent(46%) patients had DNA aneuploid patterns that did not seem to be a good prognosticator for survival. Patients whose tumor showed a high proliferative activity(S+G2/M>22%) did not die earlier. The response rate to therapy did not depend on DNA ploidy or proliferative activity. These results indicates that DNA content or proliferative activity is not the independent prognostic factor in small cell lung cancer.