We conducted a randomized phase II trial of two different schedules of topotecan in patients with advanced-stage non small lung cancer (NSCLC) without prior cytotoxic chemotherapy. All patients had histologic or cytologic confirmation of stage IV (M1) or III-B NSCLC. Patients were stratified by performance status, stage and weight loss. Patients were randomized to receive topotecan at intravenous doses of 1.5 mg/m(2)/day over 30 min for 5 days every 3 weeks (Arm A) or 1.3 mg/m(2)grade 3 in both arms included leukopenia, thrombocytopenia, malaise, constipation, diarrhea, lethargy, pulmonary, vomiting, infection and myalgia. Severe (> or = grade 3) thrombocytopenia occurred in 15.8% of Arm A patients and 37.8% of Arm B patients and this difference was statistically significant (P=0.03). The median times to progression are 101 and 63 days (P=0. 75) and the median survival times are 257 and 179 days (P=0.83) for Arms A and B, respectively. These differences in time to progression and overall survival are not statistically significant. Topotecan has limited, single agent activity in advanced NSCLC when given as 1. 5 mg/m(2)/day over 30 min for 5 days every 3 weeks. We do not intend to pursue further investigations with topotecan in patients with NSCLC.