Acute myocarditis (AMC) and its sequela, dilated cardiomyopathy (DCM), are most often caused by cardiotropic viral infections in the Western world. Inflammatory cardiomyopathy (DCMi) is a specific cardiomyopathy entity of DCM, being defined by the proof of intramyocardial inflammation and/or viral infection in endomyocardial biopsies (EMBs). Diagnostic procedures of EMBs are indispensable for the etiopathogenic differentiation of the disease. Experienced cardiology centers have reported low complication rates of EMB obtainment. The histological Dallas criteria are prone to substantial sampling error and interobserver variability, have no prognostic impact and, moreover, are not suitable to select AMC/DCMi patients who favorably respond to immunosuppression. Immunohistological detection of myocarditis and viral persistence have proven adverse prognostic impact in AMC and DCM patients, respectively. This contemporary diagnostic repertoire on EMBs is essential for the selection of DCMi patients who will likely benefit from immunomodulatory treatment, which has been addressed in randomized trials. During the past decade, cardiac magnetic resonance (CMR) has developed as a valuable noninvasive diagnostic approach for the detection and localization of intramyocardial inflammation, and CMR guidelines for AMC have been elaborated. Late gadolinium enhancement (LGE) has been associated with adverse prognostic outcome in DCM patients. CMR techniques, however, are not suitable to specifically detect myocardial viral infections. To date, no classic biomarker has been shown to differentiate between DCMi and noninflammatory cardiomyopathies.