In the comparative study on the mercury distribtuion in the principal organs, blood, and urine of guinea pigs with acute sublimate poisoning, the author arrived at the following conclusions. 1. The microdetermination of mercury has been conducted by a modified method of the Dithizone method. By properly eliminating Cu io which becomes an obstacle and by paying a sufficient precaution to the preparation of the reagent as well as to the determination procedures, a high sensitivity will be attained and for the microdetermination of mercury contained in organic substances such a method will prove to be an excellent one. 2. The kidneys are proven to show a great affinity to mercury, revealing a marked adsorption of mercury. In addition, the urine as an excretory carrier presents a relatively large amount of mercury next to the kidneys. 3. In the spleen and caecum likewise a considerable amount of mercury has been adsorbed, followed by the heart, lungs, large intestines, Small intestines, and stomach in the order mentioned. 4. The amount of mercury adsorbed in the liver and blood is insignficantly small. 5. The total amount of mercury contained in the urine, blood, as well as in the principal organs is greatest in the kidneys, followed by the urine, caecum, large intestines, liver, blood, small intestines, lungs, heart, stomach, and spleen in the order mentioned.