Current recommended treatments for long-chain FAO disorders essentially relies on dietary approaches, with restriction of long-chain fat intake along with medium-chain triglyceride supply (MCT oil). A carbohydrate-rich diet also improved exercise tolerance in CPT II-deficient patients, as indicated by lowering of perceived exertion and an increased duration of exercise after such a diet (Ørngreen et al., 2003). More recently, a remarkable improvement of cardiac and muscular symptoms occurred in three children with VLCAD deficiency, after dietary supplementation with a seven-carbon medium chain fatty acid (triheptanoïn). The mechanism underlying this effect is believed to involve the production of C5 ketone bodies and propionyl-CoA, which allows for replenishment of the pool of catalytic intermediates for the citric acid cycle (Roe et al., 2002). This promising approach is still under evaluation and marked digestive side effects could restrict its indication towards the more severe form of FAO defects. Pharmacological approaches are mainly carnitine supplementation in order to provide carnitine to convert potentially toxic long-chain acyl-CoAs to acylcarnitines. However, the role of carnitine supplements in FAO defects remains controversial and of unproven value due to the absence of controlled trials.