The amounts of gold and copper present as impurities in 500 Greek silver coins of the fifth century B.C. have been determined with a gamma-ray spectrometer, following neutron activation. The coinage from eight cities and kingdoms was studied; the average gold-content for different groups of coins varies between 0. 02per thousand and 0.3per thousand, and the copper content between 0. 1per thousand and 10per thousand. Evidence about trading connexions and of deliberate debasments of the coinage has been obtained, and several unsupected plated coins were detected. The gold content was determined by measuring the intensity of the 0.411 MeV gamma-ray from Au198 (2.69 d); for the copper content the 0.511 MeV positron annihilation radiation from Cu64 (12.8 h) was used as a check of identity. The technique of using total gamma-activity decay curves by themselves is insufficiently sensitive. For accurate work, the importance of approximate facismile standards is stressed. -- CAL