The microstructural changes of dental amalgams during aging at room temperature have been examined using a scanning electron microscope equipped with an energy dispersive x-ray analyzer. Experiments were carried out using two different types of specimens: (1) amalgam/ epsilon Cu-Sn (Cu//3Sn) diffusion couple and (2) several amalgams with variations in copper content. Structural changes that occurred on the surface, as well as in the interior, were examined. The present study revealed that some intermetallic compounds in amalgams decompose, followed by a redistribution of atoms to form more stable compounds during aging. The rate of the redistribution depends upon the phases present in the amalgam and on the types of diffusion processes that may take place.