For the purpose to elucidate changes in common immunity of cancer-bearing body after tumor removal, after transplanting 500×10(4) cells/mouse of Ehrlich ascites tumor cells to the back between the scapulae of DD mice, tumors were removed with lapse of time as thoroughly as possible, and on the 23 rd day of tumor transplantation regional axillary lymph nodes, distant mesenterial lymph nodes and spleen were removed and lymph node cells were prepared from them and these cells were tested for their antitumor activity to JTC-11 cells (derived from Ehrlich cancer cell). The results are briefly summarized as follows: 1. In the group removed of tumors on the seventh day after Ehrlich cancer transplantation none of the tissues showed antitumor activity. 2. In the group removed of tumors on the tenth day there was observed a strong antitumor activity remaining only in the regional lymph nodes. 3. In the group removed of tumors on the fifteenth day, antitumor activity was found in practically all lymphatic tissues inclusive of regional lymph nodes. 4. In the group removed of tumors on the 20th day, antitumor activity could be observed in none of the lymphatic tissues. Considering the antitiumor activity of lymphocytes from the aspect of common immunity in cancer-bearing body, when tumor mass is removed as thoroughly as possible at the time when there is sufficient antitumor activity, such an activity remains in the body for a long time after tumor removal.