Methods: 17 decompensations in 4 adult patients with MSUD treated by parenteral mixture (group P) were compared to 18 previous decompensations treated by enteral feeding in the same patients (group E). Total amount of leucine in blood was estimated as 0.65xbody weight xleucine concentration and clearance of leucine at day 3 (D3) was calculated by initial minus D3 amount of leucine/3. Results: Mean leucine concentration at presentation was similar in the groups P and E (15.7 and 15.9 mg/dL). Mean clearance of leucine at D3 was significantly higher in the group P than in the group E (1759.4±1021.0 vs 982.2±958.5 mg/day, P=0.026), without side effect. Mean duration of hospitalisation was similar (4 vs 4.5 days, P=NS) . No patient in the group P worsened and needed to be dialysed whereas one patient was dialysed in the group E.