In patients with acute or chronic myocarditis, arrhythmias are a common and often the only clinical symptom in the natural course of the disease. The potentially malignant tachy- and bradyarrhythmias are of particular significance in the differential diagnosis of sudden cardiac death in myocarditis. Factors responsible for the increased incidence of cardiac arrhythmias are structural changes, parameters of ventricular dynamics and vascular changes. On the one hand, inflammatory processes in the cardiac myocytes and interstitium can lead directly to fluctuations in membrane potential. Fibrosis and scarring of the myocardial tissue and secondary hypertrophy and atrophy of the myocytes favor the development of ectopic pacemakers, late potentials and reentry as a result of inhomogeneous stimulus conduction. Furthermore, parameters of ventricular dynamics such as increased wall tension, increased myocardial oxygen consumption and diminished coronary reserve in the case of disturbed systolic or diastolic left ventricular function also contribute to the increased incidence of arrhythmias. Lastly, vascular factors can further increase the arrhythmogenicity of the inflamed myocardium through the disturbance of micro- and macrovascular perfusion and the resulting myocardial ischemia. Non-invasive rhythmological evaluation by 24 h Holter ECG, measurement of ventricular late potentials and heart rate variability can be used for orienting risk stratification of the at-risk patient with myocarditis. Programmed atrial and ventricular electrophysiological stimulation also has a relatively high predictive value for spontaneous ventricular tachyarrhythmias. It should be emphasized that, at the present time, optimal electrophysiological parameters with a high predictive value do not exist. In a selected patient population, immunosuppressive therapy in addition to conventional antiarrhythmic therapy can lead to the reduction or complete suppression of spontaneous and inducible arrhythmias. Nevertheless, in the interim, further precautionary antiarrhythmic measures such as serial antiarrhythmic treatment, VT ablation and ACID implantation are necessary in patients with malignant cardiac arrhythmias. Right ventricular myocardial biopsy for demonstration or exclusion of myocarditis is an important additional examination which can improve the differential diagnosis and treatment of patients with cardiac arrhythmias of unclear etiology.