The conditioned medium from B104 neuroblastoma cells (B104CM) induces proliferation of οligodendrocyte precursor cells (OPCs) in vitro, which indicates that certain factors contained within B104CM give instructional signals that direct the proliferation of OPCs. However, the OPC-proliferative factors present in B104CM have yet to be identified. Platelet-derived growth factor AA (PDGF-AA), basic fibroblast growth factor (bFGF) and insulin-like growth factor-1 (IGF-1) have been reported to act as potent mitogens for OPC proliferation. This raises the possibility that B104CM induces proliferation of OPCs through secretion of PDGF‑AA, bFGF and/or IGF-1. In the present study, we detected the expression and levels of PDGF-AA, bFGF and IGF-1 in B104 cells and B104CM, and observed the expression of their receptors in OPCs. The results indicated that these growth factors were expressed in B104 cells and B104CM. All 3 receptors, PDGFR, FGFR2 and IGF-1R, were also detected in OPCs. Furthermore, B104CM-stimulated OPC proliferation could be markedly decreased by both AG1295 (an inhibitor of PDGFR) and PD173074 (an inhibitor of FGFR). However, the inhibition of IGF-1R with AG1204 did not affect the proliferation of OPCs. Our study suggests that the PDGF-AA and bFGF in B104CM are 2 key factors that stimulate OPC proliferation.