The studies on the hemolytic action of pneumococci and streptococci have been conducted principally with the use of catalase carrier blood. Prof. Takahara has recently encountered the patients whose blood carried hardly any catalase. For the fundamental investigation for acatalasemia, some experiments have been attempted about actual hemolytic picture of some bacteria acting upon the catalase and non-catalase carrier blood. In the present report, blood of man, goat, guinea pig, and rabbit were used as catalase carrier, and that of domestic duck as non-catalase carrier. As for the bacteria, Pneumococcus type I, II and III, Streptococcus hemolyticus (Cook strain), and Streptococcus viridans have been employed for the experiments. And by measuring the catalase and peroxidase activity and respiration of each experimental materials, the following results have been obtained. 1. Erythrocytes and blood of man, goat, rabbit and guinea pig contains catalase, but there is practically no substantial difference in their contents; whereas that of domestic duck hardly possesses any catalase. 2. Peroxidase activities both in the catalase carrier and the non-catalase carrier erythrocytes and blood are approximately the same. 3. O(2) uptake during respiration of domestic duck erythrocytes are far more than those of the catalase carriers, and this can be assumed to be dependent upon the presence or absence of nuclei as well as upon the amount of stroma. 4. Catalase activities in Pneumococcus type I, II and III are negative, and are slightly positive in St. hemolyticus and St. viridans. 5. Peroxidase activities in these bacteria nearly coincide. 6. No marked differences can be found in O(2) uptake among the bacteria employed in the experiments.