From April 2 to July 9, 1989, Cancer and Leukemia Group B (CALGB) conducted a Phase II study of etoposide and carboplatin in advanced (AJC Stage IIIb-IV) non-small-cell lung cancer (NSCLC) patients whose performance status (PS) was 0-2. The combination was given at the maximum tolerated dose as defined in a prior CALGB study. Of 76 eligible patients with follow-up data, complete responses were achieved in three patients (4%) and partial responses, in five patients (7%). One patient (1%) with evaluable disease showed improvement. There was only one partial response in the PS 2 patients. Performance status was a predictive factor for response or improvement (p = 0.0368). A high incidence (74%) of severe or life-threatening hematologic toxicity and fatal sepsis in four patients was a reflection of the intensity of the chemotherapeutic regime. The median survival from study entry was 7.4 months. Thirty-seven percent of the patients survived beyond 1 year; the median survival for the PS 0-1 patients was 11.7 months for the PS 2 patients, 4.1 months. Median time to treatment failure was 3.9 months, but treatment had not failed in 9% of the patients after 1 year, all of whom were PS 0-1 at time of study entry. Although the response rate with this dose-intensive chemotherapy regimen was disappointing, the median survival of PS 0-1 patients was equivalent to that of Stage III NSCLC patients in prior CALGB studies. In patients with NSCLC who are treated with chemotherapy, PS may be as important a prognostic factor as stage, when median survival is used as an endpoint.