Oligodendrocyte Growth Supplement (OGS) is a medium supplement designed for the optimal growth of normal human oligodendrocytes in vitro. It is a sterile, concentrated (100X) solution which contains growth factors, hormones, and proteins necessary for the culture of normal human oligodendrocytes. The supplement is formulated (quantitatively and qualitatively) to provide a defined and optimally balanced growth environment that maximally promotes the growth of normal human oligodendrocytes in vitro. The supplement is designed as an additive for oligodendrocyte medium (OM, Cat. No. 1621) and should be used in conjunction with that medium.