Muscle carnitine deficiency was found in 12 children affected with Duchenne muscular dystrophy (DMD), the diagnosis being made at a preclinical stage or at the beginning of the clinical symptoms. Enzymatic activities related to fatty acid transport and carnitine metabolism were studied in these patients and normal subjects: palmitoyl carnitine transferase was increased, palmitoyl carnitine hydrolase was not found in the muscle, palmitoyl coenzyme A synthetase was normal and palmitoyl coenzyme A hydrolase was increased.