Seven patients with Rasmussen encephalitis (RE) were treated with the immunosuppressant tacrolimus and followed for a median of 22.4 months. They were compared with 12 historical untreated RE patients (median follow-up 13.9 months). The tacrolimus-treated patients had a superior outcome regarding neurologic function and progression rate of cerebral hemiatrophy but no better seizure outcome. No treated patient, but 7 of 12 control patients, became eligible for hemispherectomy. Tacrolimus did not have any major side effects.