Objectives: It was investigated the in vitro effects of EMA on respiratory parameters measured by oxygen consumption supported by succinate or glutamate/malate in mitochondria from rat brain. Material and methods: Mitochondrial fractions were prepared from brain of 30day-old Wistar rats and incubated in a medium containing succinate or glutamate/ malate. Oxygen consumption was then measured under various conditions. Results: EMA increased state 4 (25%), decreased state 3 respiration (45%) and respiratory control ratio (RCR; 55%) with succinate-but not with glutamate/malate-supported oxygen consumption. EMA-induced decrease of state 3 in succinate-supported respiring mitochondria was significantly minimized by nonselective permeabilization of mitochondrial membranes induced by alamethicin. Malonic acid (MA) also diminished state 3 (40%) and RCR (40%), but did not affect state 4 respiration with succinate as substrate. However, mitochondrial permeabilization did not affect the MAinduced state 3 inhibition. Furthermore, the respiratory chain activities were not altered by EMA under these experimental conditions. Conclusion/Discussion: It is concluded that EMA inhibits succinate uptake into brain mitochondria. Background: Short/branched chain acyl-CoA dehydrogenase deficiency (SBCADD) is a neurometabolic disorder biochemically characterized by tissue accumulation and high urinary excretion of 2-methylbutyric acid (MB) and 2-methylbutyrylglycine (MBG). Although affected patients present neurologic symptoms, the pathophysiology of the brain damage in SBCADD is not yet established.