Nerve growth factor (NGF) is a fully characterized molecule, well known for its actions in the differentiation and maintenance of peripheral neurons. However, recent studies suggest that its actions are not limited to the periphery, but may extend to the CNS. In particular, this trophic agent appears to affect development and survival of a variety of brain cell populations. Noteworthy are its actions on cholinergic neurons that degenerate in Alzheimer's disease and Huntington's chorea. However, studies of NGF receptor sites suggest that effects of NGF may also extend to non-cholinergic cell groups. Cheryl Dreyfus summarizes these data and points to future work necessary to define further the underlying mechanisms of action and to examine the function of NGF on diverse brain populations.