The central nervous system (CNS) is composed of multiple cell types formed through a process of lineage commitment and phenotypic differentiation of stem-like progenitor cells into three key cell types: neurons, astrocytes, and oligodendrocytes. The ability to isolate and culture these CNS stem/progenitors has facilitated the characterization of the molecular mechanisms that regulate this process, in the hopes of providing therapeutically effective cells to treat disease and injury. Although astroglial, and to a lesser extent some neuronal, phenotypes are robustly generated when these cultured stem/progenitor cells are induced to differentiate, oligodendrocytes that form the myelin-rich sheath that allows nerves to conduct action potentials are only formed at a low frequency. This relatively low frequency has necessitated the development of methods for quantifying oligodendroglial phenotypes in vitro, with greater precision and accuracy than the standard technique of microscopic counting by hand. Here, we describe the isolation of neural stem cells and the application of intracellular flow cytometry to quantify oligodendroglial phenotypes in cultured CNS stem/progenitor cells using commercially available kits.