THIS INVESTIGATION was undertaken to study the differences between the ocular and the subcutaneous inflammatory responses following heterologous tumor transplantation, and to determine whether such differences could account for the superiority of the ocular route as a transplantation site. That such differences do occur appears to have been taken as self-evident in many of the published reports dealing with the ocular transplantation of tumors. For example, Smirnova 1 assumed that the "agents of defense" could not act in the: anterior chamber but presented no evidence to support this hypothesis. Greene 2 stated that the eye differs from other transplantation sites in the rapidity and intensity of foreign-body reactions. Greene, furthermore, concluded that these differences account for the success of transplants in the ocular area. On the other hand, Morris and associates 3 described destruction of tumor heterotransplants in the eye by lymphocytes, plasma cells, and, occasionally, foreign body giant cells.