Abstract For the purpose to observe the effect of direct interaction of antigen with lymphocyte on the establishment of cellular immunity, immunization tests were made on mice with the formol-fixed Ehrlich ascites tumor cells and MH 134 hepatoma cells. The cells were fixed without any severe deformation of their surface antigen by treating with dilute formol solution at a low temperature. The fixed cells had negative surface charge and failed to associate with lymphocytes. They were poor in immunogenic capacity, though they had well-kept surface antigen. By treating with poly- l-lysine their negative surface charge turned to positive without impairing their surface antigen. The cells became to adhere to lymphocytes and acquired an extremely high immunogenic capacity.