Lesch-Nyhan syndrome is characterized clinically by mental retardation, choreoathetosis, spastic cerebral palsy, and aggressive, self-mutilating behavior. It is transmitted as an X-linked excessive character in which the primary expression of the mutant gene is in the activity of the enzyme hypoxanthine guanine phosphoribosyltransferase (HGPRT). Metabolically, the disorder is characterized by hyperuricemia and increased amounts of uric acid in the urine. There is enormous overproduction of purine de novo. Treatment with allopurinol therapy is effective in the management of those aspects of the disease that are common to this condition and gout in the adult. Treatment is not available which is effective against the cerebral manifestations of the disease.