A study of 187 surgical specimens of tumors of patients with non-small-cell lung carcinomas was carried out by means of flow cytometry. Eighty-four percent of the tumors were classified as tumors with abnormal DNA stemlines (DNA aneuploidy). Patients with tumors demonstrating DNA aneuploidy had significantly shorter survival times than those with tumors demonstrating DNA diploidy (p = .009). Cell cycle analysis was possible in 122 tumors. Patients whose tumors had 0-8% S-phase cells died later than patients whose tumors had 9-16% S-phase cells (p = .018). In addition, patients with tumors with a low fraction of labeled S-phase cells (autoradiography) had a better prognosis than patients with tumors with a high proportion of labeled S-phase cells (p = .041).