CI-581(a phencyclidine derivative), a new potent, short-acting nonbarbiturate was administered to 101 patients, ranging in age from 2 months to 68 years, either intravenously, intramuscularly, or by a combination of the two routes. An intravenous dose of 1 to 2 mg per kg of body weight produced surgical anesthesia within 30 seconds, and adequate operating condition lasted for 5 to 20 minutes. With the onset of anesthesia, eyes usually opened and extremities became relaxed. However, pharyngeal and laryngeal reflexes remained active, and airway remained patent without benefit of manual support or the insertion of a mechanical airway. The pulse rate usually increased and the blood pressure rose sometimes to undesirable levels following intravenous administration, To achieve surgical anesthesia by intramuscular route a dose of 5 to 10 mg per kg was required. Surgical anesthesia developed in 3 to 5 minutes and lasted for 20 to 30 minutes. Some of the patients remembered the experience of dream which was of colorful and cheerful nature. There was no serious postoperative complications. CI-581 seemed useful to produce anesthesia for short procedures particularly in infants and children with intramuscular administration.