Hypocretin/orexin deficiency appears to be a consistent feature of narcolepsy with a putative autoimmune mechanism involved. We treated four hypocretin/orexin‐deficient narcolepsy patients with intravenous immunoglobulins and assessed the efficacy by repeated polysomnographies and questionnaires. Three patients received the treatment within a few months after acute onset of narcolepsy. A clear improvement in the frequency and severity of cataplexy was obtained with a benefic effect up to 7 months without any anticataplectics drugs at follow‐up. Our findings point to the importance of early diagnosis of narcolepsy, which once treated quickly may modify its long‐term outlook. Ann Neurol 2004;56:905–908