A patient is described in whom dizzy spells and cardiovascular syncope occurred due to a tachycardia - bradycardia syndrome over a period of ten years. Eventually permanent atrial standstill developed, characterized by a slow supraventricular rhythm without "P" wave activity, absence of "a" wave in jugular venous pulse, immobility of the atria on fluoroscopy and refractoriness to electrical atrial stimuli. The etiology of atrial paralysis in this case remains unknown; the etiopathogenesis of this rare disorder is discussed. Since "on demand" ventricular pacemaker insertion the patient has been well and his exercise tolerance has significantly increased.
