Adjuvant chemotherapy is now standard therapy following resection of large or locally advanced non-small cell lung cancer (NSCLC), with improvement in survival demonstrated in multiple randomized trials. Despite this, disease recurrence following optimal surgery and adjuvant systemic therapy is common. For patients with locally advanced disease, the majority will have a recurrence within the chest, most commonly at the bronchial stump or in hilar or mediastinal lymphatics. Postoperative radiation therapy (PORT) has been shown to decrease local and regional recurrences, an effect noted most clearly in stage N2 patients and those with positive surgical margins. An improvement in overall survival, similar to that following adjuvant chemotherapy, has not been consistently noted due to a high risk of treatment-related normal tissue toxicity in trials conducted over several decades. Improvements in radiation technique appear to have decreased the toxicity of PORT in more modern series, presumably increasing the potential benefit.