Quantum dots (QDs) are highly promising nanomaterials in bioimaging system because of their bright fluorescence, broad UV excitation, narrow emission band, and high photostability. Recently, there is a great activity on Ag2S quantum dots for both imaging and drug/gene delivery due to the potential of having a better cytocompatability and near infrared luminescence. 2-Mercaptopropionic acid (2 MP A)-coated silver sulfide (Ag2S) QDs were reported as the most luminescent, stable, anionic Ag2S QDs in the literature. In this study, we aim to determine the cytotoxicity of 2 MP A/Ag2S in Chinese hamster lung fibroblast (V79) cells. The genotoxic and apoptotic effects of 2 MP A/Ag2S QDs were assessed by the alkaline single cell electrophoresis assay and real time polymerase chain reaction techniques, respectively. The cell viability decreased above 200 mu g/ml and 800 mu g/ml for MTT tetrazolium and neural red uptake assays, respectively. DNA damage was not observed by 2 MP A/Ag2S QDs at the studied concentration levels (5-2000 mu g/ml). The levels of mRNA expression of p53, caspase 3, caspase 9, box, bcl-2, survivin were not changed by 2 MP A/Ag2S QDs below IC50 (around 1000 mu g/ml). Hence, 2 MP A/Ag2S QDs did not show any cytotoxic or genotoxic effects in V79 cells at lower doses. We conclude that the biocompatibility of 2 MP A/Ag2S ODs makes them suitable for cell labeling applications.