In a prior Cancer and Leukemia Group B (CALGB), 16% of a small cohort of patients with extensive small call lung cancer who had failed to obtain a complete remission with chemotherapy did obtain a complete remission after therapy with interleukin-2 (IL-2). In this current trial, 10 patients with extensive small cell lung cancer who had had no prior therapy were treated with subcutaneous IL-2 as induction therapy and then standard chemotherapy with etoposide/cisplatin. Only one patient experienced an objective response to the IL-2 administered prior to chemotherapy. The factors governing response to IL-2 in the first trial but not in this trial are discussed.