OBJECTIVE Camphorquinone (CQ) is cytotoxic in cell cultures. The mechanism of this toxic action, however, is not yet clearly understood. Aim of this investigation was to analyze the effects of non-irradiated CQ on intracellular formation of reactive oxygen species (ROS), intracellular glutathione (GSH) content, and the integrity of DNA in cultured primary human gingival fibroblasts (HGF). METHODS Cells were exposed to CQ at concentrations ranging between 0.05mM and 2.5mM. Intracellular levels of ROS were detected by the fluorescent probe 2',7'-dichlorofluorescein diacetate (DCFH-DA) and GSH was determined by the fluorescent probe monobromobimane (MBBr). Genotoxicity was measured quantitatively by the alkaline comet assay. The cytotoxic effects of CQ were investigated by means of the fluorescent dye propidium iodide and the Cytotoxicity Detection Kit. RESULTS CQ generated an increase of intracellular ROS, a depletion of intracellular GSH level, decreased cells' viability and total cell number dependent on the applied CQ concentration: 0.5-2.5mM (ROS upward arrow, GSH downward arrow) and 0.125-2.5mM CQ (cytotoxicity upward arrow). Increased DNA damage was observed at all concentrations (0.05-2.5mM, p<0.05). The ROS-scavenger N-acetylcysteine (NAC) reduced CQ-induced ROS formation at CQ concentrations higher than 0.5mM (p<0.05). CONCLUSIONS Our data indicate that non-irradiated CQ induces oxidative stress, DNA damage and cytotoxicity as well in primary HGF.