Churg-Strauss syndrome and Wegener granulomatosis are the two principal ANCA-associated vasculitides. Cardiac damage is frequent and prognosis poor. This damage is often subclinical initially and undetectable with standard cardiac imaging techniques (such as cardiac ultrasound or myocardial scintigraphy). Cardiac MRI permits early diagnosis of the different types of cardiac damage (myocarditis, pericarditis, and impaired myocardiac perfusion) that may occur during ANCA-associated vasculitis, even before the onset of symptoms. Early detection of this cardiac damage is crucial for it enables faster implementation of aggressive treatment, which may significantly improve disease prognosis. The widespread, even routine, practice of cardiac MRI in patients with ANCA-associated vasculitis thus seems justified, for this noninvasive examination provides essential diagnostic and prognostic information and helps guide therapeutic management.