This article briefly reviews the clinical aspects and rationale for therapy with l-deprenyl for several neuropsychiatric conditions, including major depression, Alzheimer's disease, and Parkinson's disease. The rationale for the use of l-deprenyl in these conditions is discussed, and evidence for efficacy is reviewed. Lastly, there is a review of the lack of evidence for l-deprenyl's abuse potential and its use as putative nonspecific cognitive enhancer, a so-called "smart drug." Although l-deprenyl itself appears to have no abuse potential, it is theoretically possible that it might potentiate the actions and frequency of dosage and use of various drugs of abuse or dependence. This is as yet an underresearched area, and more work is required.