In order to evaluate the effect of different doses of penehyclidine hydrochloride (penehyclidine) on heart rate (HR) and HR variability (HRV) in hysteroscopy, 180 patients (American Society of Anesthesiologists grade I-II) were randomized equally to three groups: 0.5 mg penehyclidine and intravenous anesthesia (group I), 1.0 mg penehyclidine and intravenous anesthesia (group II) and saddle anesthesia combined with intravenous anesthesia (control group). HR and HRV, including total power (TP), low-frequency power (LF), high-frequency power (HF) and the LF to HF ratio (LF/HF), were recorded prior and subsequent to the induction of anesthesia (T(0) and T(1), respectively), following the start of surgery (T(2)) and following completion of surgery (T(3)). HR was lower at T(2) than at T(0) in the control patients, but no differences were observed in groups I and II. The HR at T(2) was increased in group II compared with that in group I. TP in group II was significantly higher compared with that in group I at T(2). At T(1) and at T(2), the LF and HF values were lower in group I than those in the controls. Patients in group II also had higher LF and HF at T(2) than patients in group I. The HF was higher at T(2) than that at T(0) in the controls; however, the HF and LF did not change significantly within groups I and II. No significant differences were observed in the LF/HF ratio among the three groups. At a dose of 0.5 mg, penehyclidine stabilized HRV and did not alter the autonomic nervous modulation of HR. A penehyclidine dose of 1.0 mg may be superior to a dose of 0.5 mg in maintaining HR, but is less effective at balancing sympathetic and parasympathetic activity.