In a period of 8 weeks, a randomized, double-blind clinical trial was carried out to compare the effects of carnitine and placebo on improving fatigue symptom in MS patients. Patients with relapsing-remitting MS, with Expanded Disability Status Scale (EDSS) less than 4.0, MS related fatigue with a Fatigue Severity Scale (FSS) >4, who had been receiving interferon β therapy for at least one year, were included. Patients with symptoms of depression, relapse within previous 8 weeks were excluded. Eligible patients were randomly assigned to one of two groups after obtaining written informed consent. one group received 1000mg/d carnitine and one group received placebo. A total of 66 patients were assessed at the beginning of the study and after 8 weeks using Fatigue Severity Scale (FSS).