Experiments were performed on male Sprague-Dawley rats to investigate the immunobiological effects on route of administration of amygdalin(AM). Rats were administered orally at 12.5, 25, or 50mg/kg/day of AM or injected wtih 25,50, or 100mg/kg/day of AM intravenously for 2 weeks. Rats were immunized and challenged with sheep red blood cells(SRBC). The results of this study were summarized as follows;(1) In oral administration of AM, body weight gains were significantly increased by 50mg/kg AM as compared with controls, the relative weights of liver and thymus also were significantly increased by 12.5 and 25mg/kg AM. However, 2-mercaptoethanol-resistant hemagglutination titier (2-MER HA), Plaque forming cells (PFC) and rosette forming cells (RFC) were non-dose dependently decreased. Phagocytic activity and delayed-type hypersensitivity (DTH) reaction also were significantly decreased by 50mg/kg AM. (2) In intravenous injection of AM, body weight gains, hemagglutination titer (HA), 2MER-HA, DTH reaction, PFC, RFC and circulating leukocytes were not influenced by AM. However, the relative weights of liver, spleen and thymus were significantly enhanced 100mg/kg AM. These results indicated that oral administration of AM non-dose dependently suppresses humoral and cell-mediated immunity in SD rats, and that intravenous injection of AM is unaffected humoral and cell-mediated immunity, however, the high dose of it significantly enhances phagocytic activity.