Background Rocuronium's rapid onset and intermediate duration of action with intravenous administration suggests that intramuscular administration might facilitate tracheal intubation without producing prolonged paralysis. Accordingly, in infants and children, the authors measured onset at the adductor pollicis and respiratory muscles to determine the optimal dose (phase I), then gave this optimal dose to determine the optimal time for tracheal intubation (phase II). Methods The authors studied 45 unpremedicated patients aged 3 months to 5 yr. In phase I, 25 patients were anesthetized with nitrous oxide and halothane and breathed spontaneously; twitch tension and minute ventilation were measured. Rocuronium (800–2,400 micro gram/kg) was injected into the quadriceps or deltoid muscle; doses varied, using an “up‐down” technique, the goal being to bracket the dose depressing twitch 75–90% within 5 min. In phase II, deltoid injections of the optimal dose from phase I (infants: 1,000 micro gram/kg; children: 1,800 micro gram/kg) were given to 20 patients anesthetized with 0.82–1.0% halothane. Tracheal intubation was attempted 1.5–3.0 min later; time to tracheal intubation was varied, using an “up‐down” technique. Results In phase I, 5 of 7 patients given quadriceps injections (1,200–2,200 micro gram/kg) had slow onset of twitch and ventilatory depression. With deltoid injections (800–2,400 micro gram/kg), all patients developed complete twitch depression; median time to 50% depression of minute ventilation was 3.2 min in infants and 2.8 min in children. In phase II, intubating conditions were consistently adequate or good‐excellent at 2.5 min in infants and 3.0 min in children. Initial twitch recovery was at 57+/‐13 min (mean+/‐SD) in infants and 70+/‐23 min in children. Conclusions Deltoid injections of rocuronium, 1,000 micro gram/kg in infants and 1,800 micro gram/kg in children, rapidly permit tracheal intubation in infants and children, despite a light plane of anesthesia. Duration of action of these large doses might limit clinical utility.