We have developed a four-part protocol to differentiate human embryonic stem cells (hESCs) to oligodendrocyte progenitor cells (OPCs) according to developmental principles. In the first 2 weeks, hESCs are induced to differentiate into neuroepithelial cells, which form neural tube-like rosettes. In the following 10 d, these neuroepithelial cells are specified to OLIG2-expressing progenitors in the presence of retinoic acid (RA) and sonic hedgehog (SHH). Upon treatment with fibroblast growth factor 2 (FGF2) for another 10 d, these progenitors convert to OLIG2 and NKX2.2-expressing pre-OPCs. Finally, the pre-OPCs take 8-9 weeks to differentiate into OPCs, which express additional markers of oligodendrocytes, such as SOX10, platelet-derived growth factor receptor alpha (PDGFRalpha) and NG2. The unique aspects of the protocol are the use of FGF2 to promote the differentiation of gliogenic pre-OPCs in the third part and the removal of FGF2 during the transition of pre-OPCs to OPCs. This 3-month differentiation protocol consistently yields OPCs of high purity capable of producing myelin sheaths in vivo.