Macrophages are recognized to be one of the key cell types involved in inflammation. In this study, the biocompatibility of two dental implant materials, i. e., glass-ceramic (bio-active) and titanium (bio-inert) was investigated by testing the activation of two murine macrophage-like cell lines of G 3 and XC as well as thioglycollate-elicited peritoneal macrophages. The cells were cultured on the test materials for 48h, and then various biologic parameters of the macrophages, such as acid phosphatase activity (ACP), phagocytic activity and IL-lα production, were analyzed. ACP and phagocytic activity expressed by G 3 and XC cells cultured on glass-ceramic and titanium did not exceed the basal levels, and the activities induced on glass-ceramic were lower than those on titanium. Neither material inhibited the proliferation of the cell lines. The production of IL-lα by thioglycollate-elicited peritoneal macrophages, cultured on glass-ceramic, was less than that on titanium or by control cells. In contrast, the gold-palladium-silver alloy used as the control material predominantly inhibited the proliferation of G 3 and XC cells and reduced their viability. Furthermore, this material markedly increased ACP and IL-la production by peritoneal macrophages with accompanying morphological changes.We conclude that both of the present implant materials, especially glass-ceramic, produce only weak stimulation of macrophages, suggesting that they would be suitable for dental implantation.