Pathological studies were undertaken in three tumor-host models which were subjected to cortisone based treatments. The first model was Fisher 344 rats with established orthotopically implanted syngeneic bladder tumor. Cortisone-herapin and cortisone-maltose tetrapalmitate (MTP) treatments induced focal areas of tumor necrosis and necrobiosis, whereas cortisone alone caused necrobiosis. The second model was C3HBA mammary tumor fragments implanted subcutaneously in syngeneic MTP responder C3H/HeN and MTP non-responder C3H/HeJ female mice. Only cortisone-MTP treatment led to an absence of capillary extension from surrounding blood vessels into the scant tumor stroma. The third model, ethyl carbamate induced primary lung cancer in AJ mice, was tested only with cortisone-herapin combination. The treatment caused central zones of necrosis.