OBJECTIVE: To investigate whether supplementation with branched-chain amino acids (BCAAs) may improve recovery of patients with a posttraumatic vegetative or minimally conscious state. DESIGN: Patients were randomly assigned to 15 days of intravenous BCAA supplementation (n=22; 19.6g/d) or an isonitrogenous placebo (n=19). SETTING: Tertiary care rehabilitation setting. PARTICIPANTS: Patients (N=41; 29 men, 12 women; mean age, 49.5+/-21 y) with a posttraumatic vegetative or minimally conscious state, 47+/-24 days after the index traumatic event. INTERVENTION: Supplementation with BCAAs. MAIN OUTCOME MEASURE: Disability Rating Scale (DRS) as log(10)DRS. RESULTS: Fifteen days after admission to the rehabilitation department, the log(10)DRS score improved significantly only in patients who had received BCAAs (log(10)DRS score, 1.365+/-0.08 to 1.294+/-0.05; P<.001), while the log(10)DRS score in the placebo recipients remained virtually unchanged (log(10)DRS score, 1.373+/-0.03 to 1.37+/-0.03; P not significant). The difference in improvement of log(10)DRS score between the 2 groups was highly significant (P<.000). Moreover, 68.2% (n=15) of treated patients achieved a log(10)DRS point score of .477 or higher (3 as geometric mean) that allowed them to exit the vegetative or minimally conscious state. CONCLUSIONS: Supplemented BCAAs may improve the recovery from a vegetative or minimally conscious state in patients with posttraumatic vegetative or minimally conscious state.