It is apparent from the foregoing discussion that carnitine plays an essential role in human intermediary metabolism. The question of a dietary requirement for carnitine, particularly for the human infant, is of significant theoretical and practical interest. Aberrant carnitine metabolism resulting from abnormal genetic or acquired conditions may have serious consequences for the affected individual. At present many of the treatment modalities for carnitine deficiency are empirical. Further clarification of the mechanisms by which carnitine depletion is manifest in these conditions is essential for designing treatment programs. Moreover, therapeutic use of carnitine in several human diseases not involving carnitine deficiency per se has been indicated. Before such treatment becomes generally accepted, we must determine precisely the role of this amino acid in the biochemical and physiological events that participate in the pathogenesis of each disease.