Recent advances in the understanding of the physiological role of nerve growth factor (NGF) have raised the question of whether neurotrophic factors might have clinical potential in the treatment of neurodegenerative disease or nerve trauma. Although NGF was first characterized as a target-derived survival factor for developing sympathetic and sensory neurons, it is now clear that it plays an important role in the maintenance and regeneration of mature peripheral neurons. However, the highly restricted specificity of NGF for sympathetic neurons, subpopulations of neural-crest-derived sensory neurons, and striatal and basal forebrain cholinergic neurons has, for almost two decades, stimulated the search for other neurotrophic factors that might act on the many classes of neurons that do not respond to NGF. In this article, the biology of the recently discovered NGF-related family of neurotrophic factors and ciliary neurotrophic factor and their receptors are reviewed, especially in the context of the therapeutic potential of these factors in the treatment of neurological disorders of the CNS.