Young BUF rats of similar ages were inoculated with the transplantable Morris hepatoma No. 7777. At 4 weeks after inoculation, 1 group was given total iv (parenteral) feeding at high caloric and nutritional levels for 2 weeks. Such total iv feeding (hyperalimentation) of rats stimulated a more rapid tumor growth in the host. In addition, the tumors from rats fed parenterally for 2 weeks had higher mitotic activity and larger areas of necrosis, which indicate that iv feeding caused the tumor to undergo faster cell turnover with greater cell production and cell loss. Analysis of organ weights showed that parenteral feeding caused atrophy of the intestines, whereas spleen weights of the hepatoma-bearing rats fed iv were greater than those of the orally fed hepatoma-bearing rats.