Elements that caused cytotoxicity of high-noble, noble, and silver-based dental casting alloys were identified by correlating the release of elements with the cytotoxicities of the alloys. Release of elements was determined by atomic absorption spectroscopy, and the cytotoxic effect was determined by cellular mitochondrial function. The high-noble alloy released low levels of elements that did not increase after 6 hours, whereas the other alloys released higher levels of elements that increased over time. The cytotoxic effects of the alloys were attributed primarily to the release of silver and copper. In some observations, interactions between silver and copper were suspected of having an effect on the cytotoxicity.