AbstractAntibodies specific for the surface of oligodendrocytes were prepared by incubating living cultures of pure oligodendrocytes with a crude anti‐oligodendrocyte antiserum. These specific antibodies, when used in the technique of immunoelectroblotting, led to the characterization of at least two major plasma membrane proteins of 43 kilodaltons (kDa) and 53 kDa, respectively, as accessible at the external surface of the oligodendrocytes. The 53‐kDa protein was also found in oligodendrocyte‐conditioned medium in significant amounts. Additional oligodendrcyte surface proteins were also detected in the Wolfgram protein fra