1. When H(2)S(35)O(4) is administered to normal rabbits, 64.1 per cent of the radioactive sulfuric acid is excreted in the urine within 12 hours, 71.7 per cent within 36 hours, and the greater majority of it (73.1%) is excreted within 84 hours. Even in the case administered concomitantly with phenol, similarly 60.2 per cent of H(2)S(35)O(4) is excreted within 12 hours, 69.2 per cent within 36 hours, and 71.9 per cent within 84 hours. 2. In the case where phenol is administered concomitantly with H(2)S(35)O(4), there can be seen no great difference in the total radioactivity of sulfuric acid excreted as compared with that in the case given no phenol, showing an increase in the radioactivity of organic sulfuric acid and a decrease in the same of inorganic sulfuric acid. In other words, organic radioactive sulfuric acid is synthesized from the inorganic radioactive sulfuric acid administered. 3. The rate of flow (Rf) shown by the spot where the radioactivity is located on the paper chromatography in developing the urine obtained from the guinea-pigs administered phenol and H(2)S(35)O(4) concurrently coincides with the spot developed with Diazo reagent on the paper chromatography of the normal guinea-pig urine admixed with phenol-sulfuric acid. Namely, the organic sulfuric acid excreted in the urine after the concomitant administration of phenol and H(2)S(35)O(4) is phenol sulfuric acid.