Sick sinus syndrome is an association of sinus node dysfunction with bradycardia, pauses, sino-atrial block, chronotropic insufficiency and atrial arrhythmias. The diagnosis is essentially clinical and electrocardiographic. Prolonged ECG recordings allow a better assessment of the severity of the condition whereas electrophysiological investigations only provide complementary information which is rarely decisive in the therapeutic indications. Cardiac pacing is the treatment of choice for symptomatic patients: significant improvement in symptoms may be expected but there is no significant change in survival. Single chamber atrial stimulation or dual chamber pacing is preferable to single chamber ventricular pacing, especially with regards to the incidence of atrial fibrillation and the impact on quality of life.