This study was to evaluate the antitumor and immunopotentiation effects of Manda Enzyme (ME). Oral administration of ME (0.2ml/mouse) to tumor bearing mice significantly prolonged survival rate compared to the control group with the prolongation ratio of 40%. The inhibition ratios for the first and the second experiments were 51.8% and 26.4%, respectively. Only the spleen index was significantly increased in the MEF-treated group, but not in the control group. Gamma globulin level of the MEF-treated group was elevated when mice were injected with sarcoma-180 cells on the left groin. Activities of natural killer (NK) and lymphokineactivated killer (LAK) cells were observed by $^{51}Cr-release$ method. Activities of NK cell against YAC-1 cells were significantly increased in the MEF treated group. And LAK cell activities against P815 cells were also significantly increased in the experimental group. These observations, therefore, suggest that ME may have an anticancer effect and immunopotentiating effect in vivo.