This protocol describes how to purify oligodendrocyte precursor cells (OPCs) from postnatal rodent brains. The method utilizes an immunopanning technique to first remove unwanted cells by negative selection and then purify OPCs by positive selection and subsequent enzymatic release from the final panning plate. Included are modifications that allow for purification and culturing of OPCs from mouse instead of rat tissue and for use of optic nerves instead of whole brains. The method for isolating OPCs from whole brain can be used for isolating OPCs from any specific region of the brain, provided that the area can be dissected away from the rest of the tissue. Suggested culture media for maintaining proliferating OPCs or inducing oligodendrocyte (OL) differentiation are also described.