Abstract: The distribution of ³H in selected tissues was studied after intragastric (ig) or intraperitoneal (ip) administration of ³H-pyronaridine 30 mg/kg to mice. The major sites of distribution of pyronaridine (PND)-derived radioactivity were the liver, small intestine and its-content, large intestine and its content, kidneys, lungs and stomach. Twenty four hours after ig, 18% of the dose was found in the liver, 12% in residual carcasses, and 54% was excreted via the urine and feces. In the case of ip, 20% of the dose was present in the liver, 20% in residual carcasses ard about 40% was excreted in the urine and feces. About 20% of the dose was detected in the urine, and 34～40% was recovered from the feces during the period of 0～96 h. After then, ³H was excreted slowly. The total urinary excretion during 12 days after ig and ip was 20.83 and 24.07% of the dose, and the total fecal excretion, 40.44 and 41.24%, respectively. The slow excretion may explain the fact that pyronardine showed a residual blood schizontocidal activity in mice infected with Plasmodium yoelii.