Abstract: β-Dichroine is one of the three alkaioids isolated by Chou et al. from Dichroa febrifuga Lour., a Chinese antimalarial herb. The antimalarial activity of this alkaloid has been shown to be 50 times that of quinine. Besides, many other aspects of the pharmacology of the dichroines have been described. This paper reports a method for the determination of β-dichroine in biological materials and the absorption, distribution, and excretion of this alkaloid in rats. The biological materials (tissue homogenates, blood, urine, bile, and diluted faeces) were saturated with sodium chloride and extracted with chloroform at pH9. The chloroform layer was reacted with methyl orange reagent and the β-dichroine content deterined colorimetrically. This method was shown to possess a high degree of specificity for β-dichroine in tissues. Since normal excreta contains substances which behave similarly as β-dichroine, an eight-plate countercurrent distribution analysis was applied to study the excretion of the alkaloid. When given orally to rats,β-dichroine disappeared rapidly from the gastro-intestinal tract since one hour after a dose of 10 mg/kg only 58% of the administered dose could be recovered from the GI-tract. However, about 30% still remained four hours after administration of the drug. One hour after β-dichroine was given intravenously to a rat, the highest concentration was found in the kidneys. Moderate levels were found in the heart, spleen, liver, fat, and muscle, whereas very low levels were present in the blood. Only 16% of an administered dose was excreted in the urine in a 24-hour period. Very little was excreted in the faeces and no β-dichroine was found in the bile.