This chapter discusses the diagnosis, evaluation and management of pericarditis and myocarditis. The diagnosis of myocarditis is nearly and entirely clinical but is supported by noninvasive diagnostic methods such as cardiovascular magnetic resonance imaging and cardiac biomarkers such as troponin and CK-MB may be elevated. Cardiac MRI is a sensitive and noninvasive test to diagnose acute myocarditis. Cardiac biopsy is the gold standard for diagnosis of myocarditis and provides immunohistological evidence of an inflammatory cell infiltrate with or without myocyte damage. The management of pericarditis is based on providing symptom relief and reducing the inflammation. The treatment for myocarditis is mostly symptomatic and targeted at the underlying cause. It largely parallels the treatment of pericarditis, unless ventricular function or the conduction system is impaired. Patients with acutely decreased ventricular function should be admitted to the hospital for further evaluation.