Within the developing vertebrate nervous system, the mechanisms that coordinate neuronal subtype identity with generic features of neuronal differentiation are poorly defined. We show here that a bHLH protein, Olig2, is expressed selectively by motor neuron progenitors and has a key role in specifying the subtype identity and pan-neuronal properties of developing motor neurons. The role of Olig2 in the specification of motor neuron subtype identity depends on regulatory interactions with progenitor homeodomain proteins, whereas its role in promoting pan-neuronal properties is associated with expression of another bHLH protein, Ngn2. Both aspects of Olig2 function appear to depend on its activity as a transcriptional repressor. Together, these studies show that Olig2 has a critical role in integrating diverse features of motor neuron differentiation in the developing spinal cord.