Localization of metals in human tissue, has been observed in the electron probe microanalyzer. Tissues from seven organs, of malignant, and normal pathology, were surveyed and showed extremely high concentrations of Ca, Ti, Cr, Fe, Ni, Cu and Zn as well as occasional other metallic elements. The frequency of occurrence of metals in high concentrations appeared to be greater in malignant tissue. Electron microscopy was employed to locate metals within microtomed sections.