The review article presents the biosynthesis, metabolism, sources, levels, and general functions of L-carnitine, a naturally occurring compound widely distributed in the body. It is synthesized in the liver, kidney, and brain and carriers long-chain fatty acids into the mitochondria for beta-oxidation and energy production. L-carnitine plays an important role in the translocation of acetyl moieties from the mitochondria to the cytoplasm for acetylcholine synthesis in neurones. Other roles--include removal of excess acyl groups, peroxisomal fatty-acid oxidation, and antioxidant activity.