Neurotrophic molecules have a profound influence on developmental events such as naturally occurring cell death, differentiation, and process outgrowth. Despite their striking effects on developing neurons, a role for these molecules in the pathogenesis or therapy of neurological disease has not yet been defined. However, a variety of recent advances promise to provide the techniques necessary to assess the potential relevance of neurotrophic molecules to clinical neurology. In this article we review recent investigations into the biological effects, regulation of production, and mechanisms of action of the best characterized trophic molecule, nerve growth factor. In addition we review studies characterizing brain-derived neurotrophic factor and other putative neurotrophic molecules. Finally, we discuss how pharmacological effects of these molecules may be relevant to the therapy of disease states as well as neural regeneration.