The effects of nerve regeneration factor (NRF) on neuronal differentiation of PC12 cells and its signaling pathway are investigated by morphological observation and immunofluorescent cytochemical method, and the activity of ERK1/2 in NRF-treated PC12 cells in absence of serum is also studied by immuno-coprecipitation and Western blot analysis. The MEK1/2-specific inhibitor U0126, the broad-spectrum protein kinase C (PKC) inhibitor G6983 and tyrosine protein kinase (TPK) inhibitor genistein were used to determine the roles of the activation of ERK1/2 by NRF and the involvement of certain kinds of PKC or TPK receptor in this activation process. The results show that U0126 and G6983 inhibit the activation of ERK1/2 by NRF to different extents, while genistein has no effect on it, demonstrating that NRF remarkably induces neuronal differentiation of PC12 cells through activating ERK1/2 in a dose-dependent and time-dependent manner.