Arrhythmogenic right ventricular cardiomyopathy, also known as right ventricular dysplasia, is a genetically determined heart muscle disease associated with arrhythmia, heart failure, and sudden death. Autosomal dominant inheritance is typical. The identification of causative mutations in cell adhesion proteins has shed new light on its pathogenesis. Fibrofatty replacement of the myocardium, the hallmark pathologic feature, may be a response to injury caused by myocyte detachment. Sudden death is often the first manifestation in probands, emphasizing the importance of evaluating asymptomatic relatives for the disease. Standardized guidelines facilitate the clinical diagnosis of right ventricular dysplasia. However, familial studies have highlighted the need to broaden the diagnostic criteria, which are highly specific but lack sensitivity for early disease. Modifications have been proposed for the diagnosis of right ventricular dysplasia in relatives. Early right ventricular dysplasia is characterized by a "concealed phase" in which electrocardiographic and imaging abnormalities are often absent, but patients may nonetheless be at risk for arrhythmic events. Detection at this stage remains a clinical challenge, underscoring the potential value of mutation analysis in identifying affected persons. Serial evaluation of patients with suspected right ventricular dysplasia is recommended as clinical features may develop during the follow-up period. The onset of symptoms such as palpitation or syncope may herald an active phase of a previously quiescent disease, during which patients are at increased risk for sudden death. Greater awareness of right ventricular dysplasia among physicians and judicious use of implantable cardioverter-defibrillators may help to prevent unnecessary deaths.