Abstract: AIM: To investigate the effects of remifentanil on the heart rate (HR) and the heart rate variability (HRV) in middle-aged and elderly patients. METHODS: Eighty patients were divided into middle-aged group (45-59 years) and elderly group (≥60 years). The two groups were further randomly divided into pre-atropine group (ARM and ARO group) and remifentanil-only group (RM and RO group). Patients in ARM and ARO group were given atropine 0.5 mg (IM) 30 min before induction. IV injection of remifentanil (2 μg/kg) was given for 2 min (1 μg/kg·min) with a target-controlled infusion pump. Heart rate (HR) and low frequency/high frequency (LF/HF) were recorded before perfused remifentanil (T0), and 1 min(T1), 2 min(T2), 3 min(T3), 5 min(T5) and 7 min(T7) after perfused remifentail. RESULTS: Within groups, compared with baseline value of RM, HR and LF/HF of RM group at the other time points were significantly decreased (P<0.05). No significant difference was found in HR and LF/HF between RM group and ARM and ARO groups. Between groups, HR and LF/HF in RM and RO groups decreased significantly (P<0.05) compared with those in T1-T7 ARM and ARO groups. CONCLUSION: HR and the HRV of middle-aged and elderly patients significantly decrease following IV injection of remifentanil (2 μg/kg for 2 min) (1 μg/kg·min). However, inhibitory effects of remifentanil on the heart can be reversed by 0.5 mg atropine (IM). It is suggested that pre-treatment of atropine can prevent bradycardia of middle-aged and elderly patients to be treated with remifentanil.