Since 1984, the Respiratory Committee of the Cancer and Leukemia Group B (CALGB) has evaluated carboplatin, either alone or in combination, in five separate phase II studies for patients with inoperable non-small cell lung cancer (NSCLC). All patients had an Eastern Cooperative Oncology Group performance status of 0 to 2 and had not received previous treatment with chemotherapy. In 70 patients with stage IIIB or IV disease, carboplatin 400 mg/m2 administered intravenously once every 4 weeks produced a 16% overall response rate and an acceptable toxicity profile. Subsequently, combinations of carboplatin/cisplatin, carboplatin/etoposide, and carboplatin/vinblastine have been evaluated in similar patient groups. Response rates of 11%, 12%, and 20%, respectively, were obtained. Myelosuppressive toxicity was substantially greater with carboplatin/etoposide and carboplatin/vinblastine than with carboplatin alone. Carboplatin/vinblastine demonstrated efficacy similar to that of the cisplatin/vinblastine combination previously evaluated by CALGB for treatment of similar patients with advanced NSCLC; ease of administration and lack of significant nephrotoxicity also compared favorably with cisplatin-based therapy. In regional NSCLC patients, carboplatin 100 mg/m2/wk can be administered intravenously concurrently with 60 Gy thoracic radiotherapy given over 6 weeks. The impact of concurrent carboplatin added to a sequential chemotherapy-radiotherapy program for patients with regional NSCLC is currently under study by the CALGB Respiratory Committee.