At present, cardiac rhythm disorders such as sick sinus syndrome (SSS) or AV nodal block (AVB) are usually treated by electronic pacemakers. These devices have significant shortcomings, including lack of autonomic modulation, and the need for repetitive procedures for battery replacement or lead repositioning. Biological pacemakers as replacement or complement to electronic pacemakers have been the subject of increasing research interest. This research has resulted in many encouraging preclinical studies. Various approaches in the field of gene and cell therapy have been developed by different groups and this combined effort makes it increasingly realistic that this therapy will eventually find its way to clinical applicability. (Neth Heart J 2007;15:318-22.