OBJECTIVE: To investigate the changes in bispectral index (BIS) to determine the controllability and safety of intravenous anesthesia with propofol and remifentanil in different-aged children. PATIENTS AND METHODS: Forty cases of ASA levels I or II were divided into four groups (A group, <= three months old; B group, three months to two years old; C group, two years to six years old; and D group, six years to 12 years old) with 10 cases in each group. Propofol and remifentanil were used in anesthesia induction and maintenance. Hemodynamic changes, BIS values, and sedation scores during T1, T2, T3, T4, T5, T6, and T7, as well as spontaneous breathing recovery and extubation times, were recorded. RESULTS: Compared with that at T1, the BIS values at T2, T3, T4, T5, and T6 decreased (p < 0.01). SBP, DBP, and HR also decreased (p < 0.01). Compared with the other groups, the extubation time of A group increased (p < 0.01). At T2, T3, T4, T5, T6, and T7, the BIS values of A group were all less than those of C group (p < 0.01). CONCLUSIONS: Anesthesia is stable and safe when the same unit doses of propofol and remifentanil are administered to different-aged children. In infants under three months, the BIS values were lower, with prolonged palinesthesia time.