Olig1 and Olig2 are basic-helix-loop-helix (bHLH) transcription factors expressed in the motor neuron progenitor (pMN) domain of the spinal cord that generates motor neurons and oligodendrocytes. Olig1 is involved in the development andmaturation of oligodendrocytes. Olig2 is required for oligodendrocyte and motor neuron specification in the spinal cord. Olig1 and 2are also a markers for the most common primary tumors of the human brain are thought to be of glial cell origin. Therefore, there is diagnostic potential of Olig markers to augment identification of oligodendroglial tumors.