Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common defect in mitochondrial beta-oxidation in humans. It is estimated that in the Caucasian population 1 in 50 individuals is a carrier and 1 in 10,000 live births will be affected. The disease shows an autosomal recessive pattern of inheritance and is characterized by a wide spectrum of clinical features including developmental delay, behavioral problems, fasting intolerance, and vomiting. Patients demonstrate hypoglycemia and medium chain dicarboxylic aciduria. If untreated the disease can lead to coma and premature death.