Postoperative radiation therapy (PORT) in non small cell lung cancer (NSCLC) remains controversial. However, involved-field conformal (3D) RT has never been studied prospectively. In this study, we aim to assess the outcome of patients treated with involved-field 3D PORT with or without chemotherapy in NSCLC. From September 1996 to 2006, data from 75 patients treated with curative surgery and PORT for NSCLC were retrospectively analyzed. Median age was 58 years (range: 38-76). There were 5 patients with stage I, 22 with stage II, and 48 with stage III disease. Pneumonectomy or lobectomy was realized in 24 (32%) and 51 (68%) patients, respectively. Mediastinal lymphadenectomy was performed in all patients. Chemo-therapy was given in 15 (20%). All patients had 3D conformal planning. Median RT dose was 60 Gy, and CTV included bronchial stump and only positive nodal areas. All patients have completed full treatment. With a median follow-up of 55 months, 26 patients are alive without disease. Median overall survival time was 24 months, with survival rate of 35% at 5 years. The 5-year locoregional control and distant disease-free rates were 80% and 57%, respectively (Fig.1). Patients treated with pneumonectomy and those treated with at least 60-Gy PORT had better outcome (Fig.2). Grade 3 or more CTC v3.0 toxicity was observed only in 4 (5%) pts. We conclude that involved-field 3D conformal 60-Gy PORT improves locoregional control without increasing lethal toxicity.