BACKGROUND: Rocuronium is suitable for short operations and rapidly controlling the airway on account of its rapid onset and intermediate action. However, the intravenous administration of rocuronium can cause pain and withdrawal movement in children. This study evaluated the effect of diluting rocuronium from 10 mg/ml to 1 or 0.67 mg/ml with 0.9% NaCl on the withdrawal response associated with the intravenous administration of rocuronium with the intubation dose. METHODS: Ninety pediatric patients undergoing general anesthesia were randomized into one of three groups; Group OR (only rocuronium 0.6 mg/kg, n = 30), Group SR10 (rocuronium 0.6 mg/kg diluted with 0.9% NaCl to 1 mg/ml, n = 30), Group SR15 (rocuronium 0.6 mg/kg diluted with 0.9% NaCl to 0.67 mg/ml, n = 30). After the loss of consciousness by a thiopental sodium 5 mg/kg injection, the patients from each group received the 0.6 mg/kg premixed rocuronium, respectively. Patients' withdrawal response to the injection were graded using a 4-point scale (Grade 0, 1, 2, 3). RESULTS: The incidence and the intensity of the withdrawal response were significantly lower in the SR10 and SR15 groups than in the OR group (P < 0.05). In the SR15 group, the intensity of the withdrawal response was under grade 2 in all patients. CONCLUSIONS: Diluting rocuronium to 0.67 mg/ml is a simple and effective method for preventing withdrawal movements during an intravenous rocuronium injection.