Forty-two patients with stage IIIA (bronchoscopically T3 and/or bulky N2) and stage IIIB NSCLC were treated with concurrent chemoradiotherapy (CRT). Treatment consisted of CDDP, 20 mg/m2 and etoposide, 40 mg/m2 by continuous infusion (day 1-5) of weeks 1 and 5 simultaneously with chest radiotherapy (RT), 50 Gy, 2 Gy/Fx, 5 Fx/week. Surgery was attempted 3-5 weeks after RT in pts clinically downstaged. Between 10/90 and 12/92, 43 previously untreated pts were enrolled and 42 were eligible. Pts characteristics were: male/female = 37/5; mean age, 61 yrs (range, 31-74 yrs); stage IIIA/IIIB = 10/32; 15 adenocarcinoma, 24 squamous cell, 2 large cell, 1 unclassified; PS 0/1/2 = 11/24/7. Excluding 1 ineligible pts, 42 pts were evaluated for CRT response. The response rate was 81% (1 CR, 33 PR, 5 NC, 1 PD, 2 NE). Clinical downstaging was achieved in 20 pts (48%). Twenty-one pts (50%) received surgery and 19 of them were completely resected. In 7 resection specimens, no tumor was observed. Toxicity of CRT was well tolerable (Grade 4 leukopenia, 15%; Grade 2-3 esophagitis, 15%). We conclude that this intensive combined modality therapy is acceptable and appears to increase the response rate as well as resectability. Prospective randomized studies should be conducted for further evaluation of this treatment modality.