This Study was conducted to assess the single dose toxicity of DA-125, a new anthracycline anti-cancer agent, in rats and mice. The Drug was administered once intravenously to both sexes of rats and mice. Then followed a 14-day period of observation. The $LD_{50}$ Values (95% confidence limit) were estimated to be 60.9 mg/kg (57.5~64.3 mg/kg) for male rats and 60.2 mg/kg (56.2~64.5 mg/kg) for female rats, and 85.8 mg/kg (81.0~90.9 mg/kg) for male mice and 84.5 mg/kg (78.2~91.9 mg/kg) for female mice. Both sexes of rats and mice given the drug revealed the clinical sign of decreased locomotor activity, emaciation, hair loss, red-dish brown urine, salivation, and watery diarrhea. In addition, body weight from the next day to the 7th day tended to be decreased slightly in rats and mice treated with DA-125. Death occurred from the next day after administration to the 12th day. Macroscopically, congestion of gastrointestinal organ, lung, and adrenal glands were found in both sexes on the dead rats and mice. Histopathological examination of dead rats manifested atrophy of spleen, hypoplasia of bone marrow, hypcplasia and necrosis of lymphocyte in thymus, atrophy of villi in small intestine (duodenum, jejunum, and ileum), hyperplasia of granular epithelium in small intestine, degeneration of germinal epithelium in testis, defer oration of tubular epithelium in kidney, and vacuolation and myolysis of myocardium in heart. Histopathological examination of dead mice revealed hypoplasia of spleen and mesenteric lymph node, local necrosis of liver, atrophy of villi in small intestine, hyperplasia of glandular epithelium in small and large intestine, degeneration of tubular in kidney, degeneration of germinal cells in testis, and slight vacuolar degeneration of myocardium in heart.