Patients with non-small cell lung cancer (NSCLC) in stage IIIA with more than minimal N2 involvement or in stage IIIB are considered unresectable. Response rates to chemotherapy for these patients are in the range of 40%. Reduction of tumor mass by induction chemotherapy may lead to resectability and to improved survival. We evaluated response rates and determined influence of induction chemotherapy on survival when followed by surgery and radiotherapy in 60 patients with primarily inoperable stage IIIA/IIIB NSCLC. The following cytotoxic regimens were used: cisplatin (100 mg/m2) and vindesine (3 mg/m2); ifosfamide (10 g/m2) and etoposide (360 mg/m2); or a combination of cisplatin (75 mg/m2), ifosfamide (6 g/m2), and etoposide (360 mg/m2). Sixty patients were treated with two to four cycles of these regimens between June 1988 and October 1992. In 40 patients chemotherapy was repeated every 4 weeks. In 20 patients chemotherapy was intensified by interval reduction to 3 weeks with recombinant human granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim) support. The median patient age was 54 years, and Eastern Cooperative Oncology Group performance status was 0 to 2. Distribution of stages IIIA and IIIB was 21 and 39 in all patients and 5 and 15 in the group treated with r-metHuG-CSF support, respectively. The overall response rate (complete plus partial responses) was 35%. In patients treated with intensified chemotherapy and r-metHuG-CSF support, the response rate was 60%. In 37 patients (61.6%) tumor was resected 4 to 6 weeks after the last cycle of chemotherapy; R0 resection was achieved in 22 patients, R1 in eight patients, and R2 in seven patients. With a follow-up of 4 to 60 months, 1-year survival in patients with tumor regression after chemotherapy and tumor resection was 82.2% versus 35.7% in nonresponders; 2-year survival of responders and nonresponders was 50.9% and 12.8%, respectively; and median survival was 23 months and 9 months, respectively (P < .001). Median survival rates for responders with stage IIIA and IIIB disease were 39 and 17 months, respectively. Median survival after response to chemotherapy and incomplete resection (11 patients) was 17 months, whereas median survival after response to chemotherapy and complete resection (18 patients) has not yet been reached. Only four patients in this group have died with a follow-up of 4 to 60 months. Of 20 patients receiving accelerated chemotherapy with r-metHuG-CSF support, World Health Organization grades 3 and 4 neutropenia occurred in five and eight patients, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)