In a multicentre randomized trial of the EORTC-ECSG, we have treated 38 chemotherapy naïve patients with advanced non-small-cell lung cancer (NSCLC) with EO9, a novel bio-reductive alkylating indoloquinone. The drug was given at two different dose schedules by a single bolus i.v. injection: arm A 12 mg/m2 weekly and arm B 22 mg/m2 every three weeks. All together 185 courses were administered (145 in arm A and 40 in arm B). The major toxicity was reversible proteinuria more frequently occurring in the three-weekly schedule (arm A 34.5% vs. arm B 62.5%). Creatinine elevation, fluid retention and pericardial or pleural effusion were also recorded in a limited number of patients. Other common toxicities more frequent in the three-weekly administration were asthenia (21% vs. 35% of cycles), nausea (15% vs. 27.5% of cycles) and vomiting (5% vs. 17.5% of cycles). Toxicities were mainly of grade I and II. No responses have been observed. Five patients (26%) on arm A and eight (53%) on arm B experienced stable disease. These doses and schedules of EO9 do not yield activity in NSCLC.