Ancient silver objects are often found to be in extremely brittle condition. This brittleness can be observed in objects which are corroded as well as on those which show little or no sign of external corrosion. The brittleness of apparently uncorroded silver objects represents an interesting metallographic problem since the silver must have been ductile at the time the object was manufactured. The embrittlement implies a drastic change in the metallographic structure. The research laboratories of the Musée d'art et d'histoire in Geneva and the Metropolitan Museum of Art in New York City are collaborating on a project to study changes in the microstructure of silver-rich silver-copper alloys from long exposure to ambient temperatures. After preliminary work on a scanning electron microscope, microhardness tests, and examination of metallurgical cross sections of silver samples dating from 500 B.C. to A.D. 1000, research is now centered on copper precipitation from the silver-copper alloy. The binary-phase diagram for the silver-copper system shows that up to 8% of the copper will remain in solution at the eutectic temperature but that the silver can hold only one-tenth percent copper at room temperature. The precipitation of copper from the super-saturated solid solution occurs rapidly at temperatures between 150° and 450°C, but very slowly below 100°C. C. S. Smith suggested that a small but visible amount of copper could precipitate even at room temperature over many centuries. This type of precipitation is called discontinuous or cellular. Precipitaion behavior of modern silver-copper alloys is discussed and compared with the observed microstructures of ancient silver samples. The possibilities and limitations of a new method of authentication by measuring the interlamellar distance between the copper-rich precipitates is treated.