Toxicity, response, and long-term results of a definitive chemotherapy/radiation therapy (RT) protocol in patients with unresectable stage III non-small-cell lung cancer (NSCLC) were evaluated. Two cycles of cisplatin-based chemotherapy were delivered before RT, and another 2 cycles were added for patients who responded to the first 2 cycles of chemotherapy. The first course of radiation covered the primary lesion and elective nodal regions, given in 2 Gy per fraction, 5 days a week for a dose of 40 Gy. Late-course hyperfractionated accelerated RT was delivered to the gross tumor twice a day for an additional 27 Gy within 2 weeks, using 1.5 Gy per fraction. Fifty-three patients with unresectable stage IIIA (N2) and IIIB NSCLC were eligible for analysis. Twelve patients developed grade 3 neutropenia, and 3 patients developed grade 4 neutropenia. Grade 2 or 3 esophagitis was observed in 14 and 2 patients, respectively, and grade 2 or 3 pneumonitis was observed in 9 and 1 patient, respectively. Six patients developed grade 2 and 1 patient developed grade 3 late lung toxicity. The median survival time was 15.5 months. Twenty-six of 53 patients (49%) have died of locoregional progression inside the thorax. The distant metastasis rate was 59.5% (22 of 37 patients) for those who did not respond to chemotherapy and 18.8% (3 of 16 patients) for those who responded to chemotherapy (P = 0.006). Late-course hyperfractionated accelerated RT combined with induction chemotherapy was well tolerated and yielded long-term results that compare favorably with those of studies using 2 cycles of induction chemotherapy and conventional fractionated RT. However, local control was still discouraging.