The aim of this study was to evaluate the cytotoxicity of cubic boron nitride (cBN), a component of surgical cutting tools. The small quantities of cBN that typically remain on implants as a result of the manufacturing process may act as abrasives, injuring tissues surrounding the implant. To determine how cBN affects cells, we treated human neuroblastoma cells (NB-1) and human articular chondrocytes (nHAC-kn) with different concentrations of cBN powder and assessed cell growth and cell survival using the methyl-thiazol-tetrazolium (MTT) assay and a fluorescence probe assay. We also assessed the effects of tungsten carbide (WC) and cobalt (Co), two common components of joint implants, on cell growth and cell survival. Both cBN and WC moderately inhibited NB-1 and nHAC-kn cell growth. However, cBN and WC did not affect cell survival, even at high concentrations (40 microg/ml). By contrast, Co affected cell survival, inducing cell death in both cell types at increasing concentrations. These results suggest that cBN may be less toxic than WC alloys containing Co.