The effect of electrical stimulation of unilateral right and left stellate ganglia (SG) on coronary hemodynamics and the cardiac surface electrocardiogram (ECG) was studied in openchest anesthetized dogs. The results were as follows: 1) Both right and left SG stimulation resulted in significant increase of mean coronary blood flow, stroke diastolic coronary blood flow, left ventricular segmental contraction, heart rate and aortic blood pressure, with decrease of stroke systolic coronary blood flow, and coronary vascular resistance, Except for heart rate and blood pressure, these changes caused by left SG stimulation were significantly greater in the left circumflex coronary artery (LCX) area than in the left anterior descending coronary artery (LAD) area. However, right SG stimulation disclosed no significant difference between the two coronary areas. Left SG stimulation increased the positivity of the T wave of the cardiac surface ECG of the LCX area and the negativity of the LAD area, while right SG stimulation increased the positivity of the T wave in both areas. The QT interval of the cardiac surface ECG was unchanged or slightly shortened, but the QT ratio by Bazzet's formula was increased in both areas by SG stimulation. The data obtained suggest that the functional distribution of right SG and left SG innervation to the ventricles is different, that the LAD area is predominantly innervated by right SG, and the LCX area is innervated equally by right and left SG. 2) Intravenous (I.V.) administration of phentolamine (0.1mg/kg/min.) resulted in no significant change in hemodynamics or ECG patterns produced by SG stimulation, as compared. with untreated animals. However, administration of propranolol (0.5mg/kg I.V.) inhibited the effect of SG stimulation on coronary hemodynamics and cardiac surface ECG. This suggests that the effect of electrical SG stimulation may be caused by catecholamine release at sympathetic nerve endings, hence, beta receptor stimulation at coronary artery areas.