Thirty-six patients with stage IIIa histologically proven non-small cell carcinoma (T3 N2 or T2 N2) underwent concomitant radiation therapy and chemotherapy before pulmonary resection. The therapy consisted of two cycles of continuous infusion of cis-platinum, 25 mg.m-2.day-1 (days 1 through 4) every 4 weeks and concomitant irradiation, 55 Gy, of the tumor and mediastinum. Two to 3 weeks after treatment, the patients were reevaluated for thoracotomy and pulmonary resection. Five patients were found to have unresectable lesions. Thirty-one patients had complete resection, 27 by radical pneumonectomy and 4 by radical lobectomy, giving a resectability rate of 86%. Complete sterilization of lung tumor and mediastinal nodes proven histologically was achieved in 10 patients (28%) and 17 patients (47%). The 3-year survival rate is 61.7% for patients who had resection. Median follow-up is 27 months (range, 6 to 61 months). The preliminary study indicates that preoperative cis-platinum and concomitant radiation therapy is tolerated, appears to increase resectability, and may improve survival in patients with stage IIIa lung cancer.