OBJECTIVE DA-125 is a novel anthracycline derivative developed by Dong-A Pharmaceutical Company, Korea. Preclinical studies have suggested that DA-125 has greater efficacy and less toxicity than doxorubicin. The maximum tolerable dose has been shown to be 100 mg/m(2 )in a phase I trial. The purpose of this phase II study was to evaluate the efficacy and toxicity of DA-125 in patients with non-small-cell lung cancer (NSCLC). METHODS Chemotherapy-naive patients with histologically confirmed measurable NSCLC which was not curable by surgery or radiation therapy because of metastasis, local invasion, or recurrence were eligible for this trial. Between May 1996 and April 1997, 20 patients entered into this trial and were treated with DA-125 administered as a 5-min intravenous infusion every 3 weeks. The dose of DA-125 was 80 mg/m(2 )during the first cycle, and was adjusted to between 60 and 100 mg/m(2) according to the observed toxicities during subsequent cycles. RESULTS Among 19 evaluable patients, there was no objective response to DA-125. Anemia, leukopenia and granulocytopenia of grade 3 or over were observed in 4%, 6% and 12% of chemotherapy cycles, respectively. There were no treatment-related deaths. With regard to nonhematologic toxicities, diarrhea, infection and elevated serum alkaline phosphatase of grade 3 or over were observed in 2% of cycles, but were tolerable and reversible. CONCLUSIONS DA-125 at these doses and in this schedule was highly tolerable, but was not active in patients with advanced NSCLC.