Sick sinus syndrome (SSS) is usually a disease of the elderly produced by idiopathic degeneration of the sinoatrial node. Its initial manifestations range from asymptomatic to nonspecific and include palpitations, fatigue, confusion, and even syncope and sudden death. Electrocardiographic evidence of SSS includes inappropriate sinus bradycardia, sinus pause or arrest, or sinus exit block. These bradyarrhythmias may alternate with tachyarrhythmias, especially atrial fibrillation, to create the tachycardia-bradycardia syndrome. The diagnosis of SSS may be established by electrocardiography or ambulatory monitoring in the majority of cases. Medications such as digoxin, beta-blockers, and calcium blockers may initiate or worsen the manifestations of SSS. Permanent pacing is indicated for symptomatic bradyarrhythmias. Progression of SSS is mostly dependent on the presence and severity of associated coronary or hypertensive heart disease.