We evaluated the effectiveness of rectally administered midazolam for preoperative sedation in 26 cases of childhood moyamoya disease. The patients, aged 5.0 +/- 1.8 yr (mean +/- SD), received 1 mg.kg-1 of midazolam 30 min prior to induction of anesthesia. The patient's level of sedation, tolerance of anesthesia face mask, and amnesia were evaluated. In 22 of 26 patients induction via face mask was performed smoothly, and excellent anterograde amnesia was observed. Remarkable complications, including hemodynamic and/or respiratory depression, were not noted. The level of sedation was significantly related to the patient's age. Although further investigation to evaluate proper dose are needed, 1 mg.kg-1 of rectally administered midazolam is useful for childhood moyamoya disease, in which crying can worsen the neurological symptoms.