The self-healing ability of cartilage after damage is poor.Until now there is no perfect method to treat cartilage injuries in clinical field.Low-level laser therapy (LLLT),which is a damage-free method,has been known since the first laser was invented.In the present study,in order to investigate the pote ntial of low-level laser irradiation in treating cartilage injuries,the effect of low-level laser irradiation (using three diff erent low-level lasers,namely 658nm,785nm and 830nm) on the proliferation of cultured chondrocytes in vitro was performed.Th e chondrocytes were isolated from the cartilages of hind legs of healthy 8-week-old SD rats and the cell proliferati on was assessed by thiazolyl blue tetrazolium bromide (MTT) assay.The results show that irradiation using 658nm laser with 5J·cm－2 could signifi cantly stimulate the proliferation of chondrocytes cultured with fetal bovine serum at 2% and 5%.All the three of the different low -level lasers (wavelengths at 658nm,785nm and 830nm) could obviously promote chondrocytes proliferation in a wavelength- different and dose-dependent manner.All the results demonstrate that low-level laser irradiation has the potential to treat cartilage injuries in vivo.