One hundred children aged between 6 months and 10 years undergoing elective urological surgery, received 0.4 mg/kg midazolam orally about 20 minutes prior to the arrival in the operation theatre. The physiological state of the children was estimated and recorded pre- and postoperatively at defined, comparable and representative circumstances by a specially developed design. In the preoperative period orally administered midazolam had only a mild or non sedative effect in 76-84% of the children, 67-88% of the small patients behaved cooperatively or passively and 70-84% showed an indifferent or euphoric state of mind. Postoperatively 57-89% of the children were markedly sedated; therefore, the estimation of behaviour and state of mind was of minor significance. The circulatory parameters were altered only minimally. Systolic blood pressure and heart rate changed slightly but significantly compared to the preoperative values the day before surgery: a preoperative increase to a maximum immediately after the insertion of the venous cannula and a postoperative maximum after recovery. Side effects were rare (hiccough 5%, vomitus 4%, laryngospasm 1%, stridor 1%). Our results suggest that oral premedication with midazolam in children can be recommended to avoid traumatic or unpleasant alterations resulting from intramuscular injections or rectal applications. Therefore, we prefer this kind of premedication in paediatric patients.