Oligodendroglia isolated in bulk from dissected white matter of lamb or calf brain can now be maintained in culture for several days. The cells remain intact and viable during this time. The in vitro incorporation of various radiolabeled precursors into lipids or proteins was examined, and its was found that oligodendroglia synthesize the lipids which are predominant in brain, and especially in myelin. They actively synthesize cholesterol, cerebrosides, sulfatides, and all of the phospholipids, especially phosphatidylcholine. In addition, they produce a variety of radiolabeled proteins, with those of high molecular weight exhibiting the most radioactivity. Thus the cells are metabolically very active in vitro and can be used as a model system to study turnover of lipids in the cell, as well as the synthesis of myelin-specific components.