SMSCs (synovial mesenchymal stem cells) isolated from TMJs (temporomandibular joints) were induced to proliferate and differentiate in vitro by bFGF (basic fibroblast growth factor) and explore the potential of SMSC differentiation into neuronal cells. In this study, the cultured SMSCs were derived from the TMJ synovial membrane of condylar hyperplasia patients and were amplified with the indicated concentration of FCS (fetal calf serum) and DMEM (Dulbecco's modified Eagle's medium) in vitro. bFGF (25 ng/ml) was applied to induced synovial cells differentiated into neuronal cells. Inverted microscopy, scanning electron microscopy, immunocytochemical and RT-PCR were used for checking the change of the induced cells. Morphology was mostly spindle; a small part was of a polygon. The undifferentiated SMSCs showed the fibroblast-like morphology; however, most of the differentiated cells were in the shape of a spindle and the rest were polygonal. Furthermore, being induced by bFGF, SMSCs can be found to be a unique long extension from the cell body under the scanning electron microscope. RT-PCR and immunocytochemical analysis was made to confirm nestin (neural stem cell marker) and NF-L (neurofilament-light or neurofilament 68-kDa mature nerve cell marker) expression in SMSCs. SMSCs can differentiate into neuronal cells when induced by bFGF. The bFGF-induced SMSCs not only changed into neural-like cells but also expressed specific markers.