Observing leukocyte motility and leukocyte phagocytosis of India-ink in the two groups of cases, the one of the which had formic acid allyl for only once and the other had daily small dosis, and studying the effect to the motility and phagocytosis of leukocyte of various drugs for infectious hepatitis, and the following results were obtained. 1. Following the administration of formic acid allyl (30 mg/kg), the leukocyte motility was accelated within one hour and thereafter depressed abruptly. On the other hand, the phagocytosis of Indiaink have dicreased after giving formic acid allyl. Both functions of leukocyte depressed markedly in the cases given increased formic acid allyl up to 50 mg/kg. 2. Following the administration of formic acid allyl, no effect to the both functions by giving Cortisone, unclear by DOCA, and an accelation and regaining of the both fnnctions were noted by giving ACTH. Regaining of the motility, not of the phagocytosis, from depressed state and further accelation were observed following the administration of 5% dextrose in water. Ferric chlorophyll preparations had the leukocyte motility regained from depressed state following the administration of formic acid allyl of 30 mg/kg, but no effect was seen after 50 mg/kg of formic acid allyl. There was no effect by ferric chlorophyll. Glucuronic acid showed a transient effect do leukocyte motility, but not to the phagocytosis of India-ink. 3. The both functions of leukocyte have markedly depressed, the maximum at 9th day in the cases who had been having formic acid allyl 10 mg/kg for 4 days. 4. In the above cases a slight improvement to the both functions of leukocyte was seen by giving Cortisone or DOCA, a distinctive improvement, on the other hand, by ACTH. 5% dextrose in water was effective only for leukocyte motility, and ferric chlorophyll demonstrated a slight effect for the both functions and so did glucuronic acid although transient for the phaocytsois.