The efficacy and toxicity of cisplatin/etoposide and carboplatin/etoposide combinations along with thoracic irradiation were prospectively assessed in patients with small cell lung cancer. Both combinations were equally effective. However, the carboplatin/etoposide regimen caused significantly less nausea, vomiting, nephrotoxicity, and neurotoxicity, and it was easier to administer. Dose intensity and treatment delays were similar in both groups. Thoracic irradiation given concurrently with chemotherapy is feasible and seems to offer a survival advantage. The relapse rate also is lower among patients who have received radiation therapy, and recurrences tended to be outside of the lung. Overall, a survival benefit was identified for patients aged between 50 and 65 years who had limited disease, good performance status, and only one metastatic site. Prophylactic brain irradiation in a subset of patients reduced brain metastasis, but the difference did not reach significance. From this trial, it is concluded that carboplatin/etoposide combination therapy is highly effective and is well tolerated by patients with small cell lung cancer. In limited disease, this combination can be given concurrently with thoracic irradiation and offers a survival advantage.