Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disease in which muscle tissue has been partially replaced by adipose or fibro-adipose tissue. Morphologic changes in the right ventricle and ventricular arrhythmias are characteristic. Pathomorphological changes should be confirmed by NMR or endomyocardial biopsy. Morphological changes ought to be found by ultrasound methods or angiographic examination. ECG exercise test, Holter monitoring, late potentials, total ventricular activation time and programmed stimulation of right ventricle are used to evaluate the risk of sudden death due to ventricular arrhythmias which is the most important problem. Those methods indicate pharmacologic or invasive therapy (RF ablation, implanted cardioverter-defibrillators), and are used to establish the effectiveness of treatment.