The release of elements from a series of palladium-copper alloys into cell-culture medium was measured using atomic absorption spectroscopy. The effect of the alloys on the succinyl dehydrogenase activity of Balb/c 3T3 fibroblasts was also measured. Palladium inhibited the release of Cu in alloys up to 70 atomic weight percent Cu. Below 70 at. % Cu, Cu release was 0.8 ug/cm2 at 72 hours. Palladium release was lower from purebPd (0.08 ug/cm2 at 72 hours from the Pd-Cu alloys containing >70 at.% Cu, where it increased to 1.2 ug/cm2. The cytotoxicity of the alloys correlated closely with the realease of Cu, becoming markedly cytotoxic above 70 at.% Cu, when Cu release was greater than 2.2 ug/cm2.