Teniposide, VM-26 (Vumon), was administered in a dose of 60 mg/m2 on days 1 to 5 every third week to 36 patients with histologically confirmed small-cell lung cancer. None had previously received chemotherapy or radiotherapy. The median age was 73 years (range, 52 to 79). Thirty-three patients were evaluable; 21 of these had local disease. Five patients had bone marrow metastases, four had liver involvement, and one CNS metastases. All patients had a performance status less than or equal to 2 before the start of treatment. Thirty patients obtained a response (90%), ten of whom had a complete remission (30%). The median duration of remission was 8+ months (range, 1.1 to 17+ months), whereas the median survival was 8.7 months (range, 1.9 to 20 months). Toxicity was primarily hematologic, with leukopenia the only dose-limiting effect. Besides alopecia, all other side effects were minimal including nausea and vomiting. We find these results provocative in regard to the response rate and the duration of response obtained as well as in reference to the dismal results that prior investigations in previously treated patients have shown. These data may indicate the need for reconsideration of the usual strategy for performing phase II trials.