In mammals, most of the twenty SOX (SRY HMG box) transcription factors are expressed during embryogenesis and play an important role in cell fate determination. We show here that SOX13 is expressed in the developing mouse brain and spinal cord from E12.5 to E15.5, where it is largely confined to the differentiating zone rather than to the proliferating zone. In particular, we found that SOX13 expression was activated in a subset of neural progenitors as they exit the cycle of mitosis, migrate away from the ventricular zone, and start to differentiate into neurons. The SOX13 protein always localized to the nuclei of the differentiating neuronal cells, consistent with a role for SOX13 as a transcription factor during neurogenesis. Our data suggest a role for SOX13 in the specification and/or differentiation of a specific subset of neurons in the developing central nervous system.