The relationship between DNA content, TNM stage, tumor size, grade, histology, and disease-free survival was assessed in a retrospective study of patients with non-small cell lung cancer who had undergone resection and complete mediastinal lymph node dissection. Flow cytometric analysis was performed on paraffin-embedded tissue of 90 consecutive patients. The patients were analyzed both as a group and by individual stage. Median follow-up was 11 months (range, 1 to 35 months). Aneuploid tumors were not significantly different from diploid tumors with regard to pathologic TNM stage (p = 0.34), size (p = 0.5), grade (p = 0.5), or histology (p = 0.34). Disease-free survival of patients with aneuploid tumors was not significantly different than that of patients whose tumors had normal DNA content (p = 0.69). DNA content did not correlate with established prognostic factors in patients with non-small cell lung cancer who underwent resection and complete mediastinal lymph node dissection.