Abstract: The concentrations of K, Ca, Ti, Fe, Cu, Zn, and Rb in liver and spleen of mice, inbred and leukemic, have been determined by the PIXE technique. The ratio Zn/Cu in the liver is changed from 3.19 for the leukemic mice to 2.66 for the normal. For leukemic mice, an obvious increase in the concentrations of Cu and Zn in the liver and Zn in the spleen, as compared to those of healthy mice, was observed. But the concentration of Cu in the spleen of the diseased mice is decreased. It is intersting to note that, allowing the swelling of spleen of the diseased mice, the total weight of Cu in the spleen appears to be constant.