Objective: (a) To study the immunological status of the laboratory colon cancer bearing host. (b) The study of supplemental immunotherapy to animals undergoing operation for lymph node positive colon cancer. (c) The evaluation of therapeutic modalities other than radical operation in the primary treatment of rectal cancer. Method: Transplantable carcinomas of the colon induced with the carcinogen 1,2 dimethylhydrazine will be used to study the immune response of the tumor-bearing animal to subcutaneously transplanted tumor. Tumor transplanted to the exteriorized colon of the syngeneic host will also be studied. Such cancers will be excised by standard radical colectomy in lymph-node positive and lymph-node-negative tumor-bearing hosts. Postoperative active-specific immunotherapy with Concanaval A-modified tumor cells and with tumor cells alone will be compared to animals undergoing operation only. Other cell surface modifiers will be employed. In vitro immunological evaluation will be conducted at all stages of tumor-bearing and treatment. Evaluation of the role of electrocoagulation in the eradication of the primary tumor, and its effect on lymph-node-positive disease will also be evaluated in this setting along with in vitro immunological testing. The benefits of Concanavalin A-modified tumor cell immunotherapy have been previously reported. Reference: Enker, W.E., Craft, K., and Wissler, R.W.: Active-specific immunotherapy with Concanavalin A modified tumor cells. Transplantation Proceedings, March 1975 (in press).