Abstract Most cardiac ischemic episodes tend to start at the end of surgery and during recovery from anesthesia. α2 adrenergic agonists are effective for this purpose. The aim of this study was to determine the efficacy of oral clonidine as premedication on cardiovascular stability during operation and to prevent cardiovascular complications after surgery. Background: Eighty eight patients enrolled in the study and randomly divided into two groups. The study group received 1mg oral clonidine and the control group received placebo, two hours before anesthesia. Systolic and diastolic blood pressures and heart rate measured and registered in 5 different times. Any change in ECG monitoring during operation and in the recovery room were registered. Also prevalence of postoperative cardiac complications during the first postoperative day was recorded. All data were analyzed with suitable statistical tests. P<0.05 was significant considered. Methods: Comparison of mean systolic arterial blood pressures between the two groups were lower at all measured times in study group excepts on arrival to the operating room (P<0.05). Mean changes of heart rates in comparable with basic data were statistically higher in control group. Frequency distribution of ECG changes during operation and also frequency distribution of postoperative cardiac complication during the first postoperative day were higher in control group. Findings: Oral low dose clonidine as premedication before anesthesia in old patients can inhibit sympathetic over activity and ECG changes during operation. Also post. operative cardiac complications were lower in study group. Conclusion: Clonidine, Intra and post. operative, complication, α2 adrenergic agonists, premedication, cardiovascular. Key words: