In separate studies, radioisotopes 65Zn and 86Rb were used to monitor trace element fluctuations from normal in C57L/J mice throughout the progression of a murine hepatoma. Amounts too small to upset normal levels were injected directly into the blood stream. After an equilibration period, the whole mouse and various resected organs and tissues were counted. Compared to normal levels, rubidium in diseased mice was lower in kidney and blood, and elevated in skin and muscle. Diseased mice showed depressed levels of zinc in skin and muscle. Large fluctuations during different stages of tumor growth were observed for various other tissues and organs of diseased mice.