The subcellular distribution of zinc was determined in plasmacytoma cells obtained from BALB/c mice maintained on zinc adequate or zinc deficient diets. In addition, the zinc distribution in the liver was determined in the presence and absence of the tumor. In plasmacytoma cells from zinc deficient mice, the zinc concentration of the cytosolic fraction was significantly less than found in the same fraction from zinc adequate controls. This decrease may relate to decreased plasmacytoma growth seen in zinc deficient mice. The cytosolic fraction from the liver of zinc deficient mice without tumor also had decreased zinc levels compared to the same fraction from control mice. In the presence of tumor there was an increase in liver zinc and protein content in ad lib and pair fed controls which was not seen in zinc deficient tumor bearing mice. These increases were associated with all subcellular fractions prepared from the control animals. The presence of TEPC-183 plasmacytoma alters zinc and protein metabolism in the host liver and these changes are dependent on the zinc status of the host.