The anterior forebrain circuit of the songbird brain has been known for some time to play a special role in song learning. Recent work has strengthened this view and has begun to describe the specific properties of this pathway. The development of the circuit early during song learning, its auditory responsiveness, and its synaptic interaction with the vocal motor pathway all suggest that it is involved in the sensory learning and auditory-motor matching essential to normal song development. Behavioral studies point to a variety of mechanisms of action of this pathway and suggest that it is one site for steroid hormonal effects on vocal motor plasticity. Investigation of the anterior forebrain circuit promises to clarify its role in learning and to elucidate the cellular mechanisms involved.