The toxic effect of azalea extract, especially on cardiovascular system, in relatively unclear. The purpose of this study is to study the possible underlying mechanism and effect of toxic ingredient of azalea on cardiovascular system. The 71 healthy rabbits were divided into 10 groups: In group as preliminary study; 4 cc of normal saline was administered intravenously (N); 0.7 gm/kg and 1.0 gm/kg of azalea extract was administered respectively in the same route, volume (A1, A2); atropine was administered intravenously (A); after pretreatment with atropine (0.04 mg/kg) to block parasympathetic system, azalea extract was injected like the above groups (AA1, AA2); normal saline, 0.7 gm/kg and 1.0 gm/kg of azalea extract were administered respectively with 0.2 cc (1:1000) epinephrine (E0, E1, E2). We measured the following indices at I minute interval during first 10 minutes and then 10 minute interval during next 30 minutes: RR interval, QTc interval, maximal systolic and diastolic pressure drop with occurring time and presence of significant arrhythmia. The results were as follows: 1. The changes of RR interval, QTc interval were significantly increased in groups by Azalea extract. The blood pressure change was significantly decreased in groups by Azalea extract. There were no significant differences according to dosage of Azalea extract. 2. The changes of RR interval, blood pressure were significant differences between administration of atropine and Azalea extract after pretreatment with atropine, but not in the change of QTc interval. 3. There were no significant differences in the change of RR interval, ATc interval, blood pressure drop according to pretreatment with atropine. 4. The interaction between epinephrine and Azalea extract was not noted by the effect of epinephrine itself. 5. The ST change by 0.7 gm/kg, 1.0 gm/kg of Azalea extract was revealed in 1 case (14.0%), 7 case (100%), respectively. 6. Most of all cases with arrhythmia, ventricular tachycardia, ventricular fibrillation, were noted in the group by epinephrine, except on case by Azalea extract (1.0 gm/kg). It was idioventricular rhythm. In conclusion, azalea extract has negative inotropic and chronotropic effect with arrhythmogenic potential possibly through direct myocardial ischemia or injury but we can't be absolutely exclusive of actions of autonomic nervous system, especially parasympathetic nervous system.