Between 1975 and 1980,101 patients with inoperable Stage IIIMO non‐small cell lung carcinoma were entered into combined radiotherapy and chemotherapy trials at Michael Reese Hospital and University of Chicago Hospital. Sixty‐four percent of the patients responded. Median survival for all patients was 8.8 months, Responders survived 13.7 months and nonresponders 4.6 months (P = 0.002). Patients treated with 4200 rad had a higher response rate than those treated with 3Ooo rad (74% versus 54%, P = 0.04) but there was no difference in survival. Although all patients with squamous cell carcinoma died by 30 months, 18% of patients with adenocarcinoma and 20% of patients with large cell carcinoma are long‐term survivors. Brain metastases occurred more frequently in patients with large cell or adenocarcinoma than in patients with squamous cell carcinoma (P = 0.02). The prognostic effect of age, initial performance status, sex, histology, and tumor extent are examined. Toxicity was substantial with a 13% treatment‐related mortality. Combined modality therapy may benefit selected patients with non‐squamous cell types, but more effective chemotherapeutic agents are needed. Prophylactic cranial irradiation in patients with large cell carcinoma or adenocarcinoma may decrease the incidence of subsequent brain metastases.