Argues that the use of the amino acid l -tryptophan as a hypnotic might avoid the problems of nonspecificity in the currently used CNS depressants because l -tryptophan is chosen on the basis of the chemistry of normal sleep rather than on a purely empirical basis. Nine author-conducted studies on the effects of l -tryptophan on sleep are reviewed. Studies in rats, normal human Ss, and Ss with mild insomnia all demonstrate that l -tryptophan reduces sleep latency. Polygraphic studies demonstrate that l -tryptophan, unlike hypnotics, does not produce distortions of sleep physiology when first administered, on long-term administration, or after withdrawal. (29 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved