Lung cancer study group at Asan Medical Center has conducted the second prospective study to determine the efficacy and feasibility of MVP chemotherapy with concurrent hyperfractionated radiotherapy for patients with stage III unresectable non-small cell lung cancer(NSCLC). All eligible patients with stage III unresectable NSCLC were treated with hyperfractionated radiotherapy( 120 cGy/fx BID, 6480 cGY/54fx) and concurrent 2 cycles of MVP(Motomycin C 6 mg/m2 , d2 & d29, Vinblastin 6 mg/m2, d2 & d29, Cisplatin 6 mg/m2 , d1 & d28) chemotherapy. Between Aug. 1993 and Nov. 1994, 62 patients entered this study ; 6(10%) had advanced stage IIIa and 56(90%) had IIIb disease including 1 with pleural effusion and 10 with supraclavicular metastases. Among 62 Ptients, 48(77%) completed planned therapy. Fourteen patients refused further treatment during chemoradiotherapy. Of 46 patients evaluable for response, 34(74%) showed major response including 10(22%) with complete and 24(52%) with partial responses. Of 48 patients evaluable for toxicity, 13(27%) showed grade IV hematologic toxicity but treatment delay did not exceed 5 days. Two patients died of sepsis during chemoradiotherapy. Server weight(more than 10%) occurred in 9 patients(19%) during treatment. Nine patients(19%) developed radiation pneumonitis. Six of these patients had grad I(mild) pneumonitis with radiographic changes within the treatment fields. Three other patients had grade II pneumonitis, but none of theses patients had continuous symptoms after steroid treatment. Concurrent chemoradiotherapy for patients with advanced NSCLC was well tolerated with acceptable toxicity and achieved higher response rates than the first study, but rather low compliance rate(7%) in this study is worrisome. We need to improve nutritional suppoert during treatment and to use G-CSF to improve leukopenia and if necessary, supportive care will given as in patients. Longer follow-up and larger sample size is needed to observe survival advantage.