DA-125, a new anthracycline antitumor antibiotic, was administered to Sprague-Dawley rats intravenously for 4 weeks to investigate the repeated dose toxicity Focal alopecia was noted in three female rats receiving 1.0mg/kg/day. In rats receiving 1.0 mg/kg/day, weight gain decreased in both sexes after first or second week. Hematological examination revealed lower counts of total leukocyte and increased numbers of platelet after second week. At terminal necropsy, atrophy of thymus and spleen was observed. Lymphocytic depletion of thymus and atrophy of white pulp in spleen were observed microscopically. A decrease in the number of hematopoietic cells in the bone marrow and degeneration of germinal epithelia in testes were also observed. These treatment-related effects were mainly confined to rats receiving 1.0 mg/kg/day. And toxic effects with microscopic changes were not observed in rats receiving 0.2 mg/kg/day or 0.04 mg/kg/day.