BACKGROUND: Various combinations of treatment modalities have been reported in stage III non-small cell lung cancer (NSCLC), however, the standard treatment modality has not established yet. Recently, the efficacy of concurrent chemotherapy and radiation therapy has been reported in locally advanced lung cancer. We evaluate the response rate, toxicity, arid survival of concurrent chemotherapy with etoposide and cisplatin(EP) arid radiation therapy for unresectable stage III NSCLC. METHODS: Between October 1995 and December 1996, 32 patients with histologically proven unresectable stage III NSCLC without, malignant pleural effusion were entered into this study. Twenty-nine patients were eligible for the response, survival, and toxicity analysis. Induction was two cycles of chemotherapy with etoposide arid cisplatin plus concurrent chest RT to 4500cGy. Resection was attempted if the clinical response offered surgical resectability. Boost radiation therapy upto 5940cGy and one cycle of EP were performed if the disease were stable or responsive but still unresectable. RESULTS: Of 29 eligible patients, 22(75.9%) showed partial response(PR). The progression free interval was 6.3months(range 1.1 to 19.5months). Surgical resection was performed in one patient The median survival was l2.1months and one-year survival rate was 50.6%. The major toxicity was leukopenia(> or = grade 3,46%) Thrombocytopenia over grade 3 was found in 1%. Radiation pneumonitis occurred in 13 patients(46%). CONCLUSION: Concurrent chemotherapy(EP) pins radiotherapy was effective and tolerable in the treatment of unresectable stage III NSCLC.