The influence of single-walled carbon nanotubes (SWCNTs) produced by radio frequency (RF) induction thermal plasma with three catalyst mixtures (Ni-Co-Y2O3, Ni-Y2O3 and Ni-Mo-Y2O3) was evaluated on the behavior of murine MC3T3-E1 preosteoblasts. After analyzing SWCNTs properties, mitochondrial enzymatic (MTS) and lactate dehydrogenase (LDH) activities as well as neutral red (NR) uptake were measured to assess the cellular viability. To ascertain that the cytotoxicity was not merely as a result of the mechanical disturbance, either SWCNTs were added on the attached cells or cells were seeded on the SWCNT-covered plates. Regardless of the catalyst mixtures used for their production, SWCNTs added on the attached cells reduced cell viability drastically in a dose-dependent manner. However, the viability of cells seeded on SWCNTs even on those produced with Ni-Co-Y2O3 was slightly decreased at 24 h and besides cells could proliferate within 48 h. Furthermore, cells were able to organize normal filamentous actin cytoskeleton and no apoptotic cells were detected in the cultures. Thus except mechanical disturbance, thermal plasma grown SWCNTs seem to induce no severe cytotoxicity on MC3T3-E1 preosteoblasts and therefore are considered promising CNTs to be studied more deeply for future applications in bone tissue engineering. Copyright © 2013 John Wiley & Sons, Ltd.