Using five depressants, namely, Serpetin, Methobromin, Ansolysen, Apresorin, and Trapon, the author estimated the contents of circulating blood-plasma, circulating blood, total body water, and intra- and extra cellular fluid in hypertensive old persons along with the lapse of time; and obtained the following results. 1. In the case of Serpetin administration it has been observed that the volume of circulating blood is slightly increased, and likewise a slight increase of blood-plasma in a greater majority; and the contents of total body water, the value of extracellular and intracellular fluid phase are all improved. 2. In the case using Methobromin, the volumes of both the circulating blood-plasma and circulating blood fluctuate about the normal value threshold, but the value of the extracellular fluid phase shows no marked change. Changes in the content of total body water and the value of intracellular fluid phase show a parallel relationship. 3. In the case of Ansolysen administration the contents of circulating blood-plasma and circulating blood show a transient decrease, but the value of extracellular phase alone shows somewhat increasing tendency. Whereas the total body water and the value of intracellular fluid phase are not markedly affected but their fluctuation is parallel with one another. 4. In the case of Apresolin administration both circulating blood-plasma and circulating blood show a strong tendency to increase. The value of the extracellular fluid phase, though not constant, shows no marked changes, while the total body fluid and the value of intracellular fluid phase, though fluctuating transiently, show a strong tendency to return to the normal level. 5. In the case of Trapon administration, the contents of circulating blood-plasma and circulating blood fluctuate slightly for a time being but return to the original values; and the total body water and the value of intracellular fluid phase, though fluctuate temporarily together, return to their original values. The value of extracellular fluid phase shows hardly any change.