Primary aldosteronism is a rare syndrome which may reault from adenoma hyperplasia or carcinoma of the adrenal cortex and may thus be amenable to surgical correction. The findings of hypertension, hypoklemia and metabolic alkalosis suggest the diagnosis. This case report is to present the possibility of cardiac arrest due to hypokalemia during surgery for primary an adrenal tumor that was causing aldosteronism. This 25 year-old male who had a long history of aldosteronism, was admitted for surgery correction. Anesthesia was induced with thiopental sodium and was maintained with nitrous oxide and halothane. While the adrenal gland was being manipulated the patient appeared to have a sudden cardiac arrest with ventricular fibrillation as seen on the monitoring EKG. Cardiopulmonary resuscitation and D.C. shock to reverse the ventricular fibrillation was carried out immediately. The rest of the scheduled operation was continued and finished uneventfully. We concluded that the cause of the cardiac arrest in this case seemed to be a preoperative hypokalemia resulting from aldosteronism which was not corrected. In addition to that, the respiratory alkslosis from hyperventilation during the anesthesia even moreso lowered the preoperative level of hypokalemia.