We measured the cellular DNA content of paraffin-embedded tumor specimens by flow cytometry from 340 cases of resected non-small cell lung cancer, and investigated the correlation of DNA content and prognosis of these cases with long-term follow-up. These 340 cases were divided into some populations according to pathological stage, histologic type, surgical curativity and N factor, and we compared the prognosis of DNA diploidy cases and DNA aneuploidy cases in each population. DNA aneuploidy cases had a significantly less favorable prognosis than DNA diploidy cases in population of stage I adenocarcinoma, stage IIIA non-small cell lung cancer and N2 cases among stage IIIA non-small cell lung cancer, all after curative operation. But in other populations, there was no significant difference in prognosis between DNA diploidy cases and DNA aneuploidy cases. In conclusion, DNA ploidy pattern is a prognostic factor for survival in patients with stage I adenocarcinoma and N2 cases of stage IIIA non-small cell lung cancer.