The most frequently used animal species in experimental cardiac electrophysiology are mice, rabbits, and dogs. Murine and human electrocardiograms (ECGs) show salient differences, including the occurrence of a pronounced J-wave and a less distinctive T-wave in the murine ECG. Mouse models can resemble human cardiac arrhythmias, although mice differ from human in cardiac electrophysiology. Thus, arrhythmia mechanisms in mice may differ from those in humans and should be transferred to the human situation with caution. Further relevant cardiovascular animal models are rabbits, dogs, and minipigs, as they show similarities of cardiac ion channel distribution with the human heart and are suitable to study ventricular repolarization or pro- and antiarrhythmic drug effects. ECG recordings in large animals like goats and horses are feasible. Both goats and horses are a suitable animal model to study atrial fibrillation (AF) mechanisms. Horses frequently show spontaneous AF due to their high vagal tone and large atria. The zebrafish has become an important animal model. Models in "exotic" animals such as kangaroos may be suitable for particular studies.