Numerous studies demonstrated the superiority of atrial based pacing modes (AAI/R, DDD/R) in the pacemaker therapy of sinus node disease. They reduce mortality, the incidence of atrial fibrillation and the risk for heart failure and increase quality of life, but there is still debate about the most appropriate mode of pacing. The AAI-mode carries the risk of high degree AV-block and the possible occurence of atrial fibrillation with slow ventricular response, demanding ventricular stimulation. DDD-pacemakers, however, are more complex and expensive and the stimulation in the apex of the right ventricle results in the loss of the normal activation sequence of the ventricles and can cause hemodynamic deterioration. Despite the lack of prospective randomized studies comparing the long term performance of the two pacing modes (AAI/R and DDD/R) many arguments plead in favour of a preferential use of AAI/R in patients eligible for permanent atrial pacing.