Mitochondrial fatty acid B-oxidation is a major source for energy prod
uction, particularly at times of stress or fasting, Inborn errors of f
atty acid oxidation have emerged during the past decade as important i
nherited causes of severe metabolic disturbances, including hypoketoti
c hypoglycaemia, cardiomyopathy, skeletal muscle myopathy, and childho
od sudden death. Since the first description in 1973, at least 14 diff
erent genetic defects of mitochondrial fatty acid metabolism have been
recognized. Our current understanding of the basic biochemistry, clin
ical presentations, and molecular bases of fatty acid oxidation disord
ers is reviewed.