The term myocarditis covers a diversity of pathological conditions. Aetiologically, the best documented is acute infective myocarditis, predominantly caused by enteroviruses, particularly Coxsackie B. However, there are many possible sources of infection, and the management of immunosuppressed patients requires careful deliberation. Research into the pathogenesis of viral myocarditis has made formidable advances and provided detailed knowledge of the mechanisms responsible for myocardial damage. Microbiological techniques have yielded evidence of the involvement of Coxsackie viruses in the development of dilated cardiomyopathy. Nowadays, the term myocarditis has a strictly histopathological definition which is clinically applicable only in the few cases where endomyocardial biopsy is performed. The diagnosis, acute infective myocarditis, can usually be made with reasonable certainty on the basis of ECG findings and the serum concentrations of biochemical markers. Physical diagnostic procedures, particularly echocardiography, can provide useful supporting evidence. Prognosis is generally good in cases of acute infective myocarditis, whereas that in other forms of myocarditis varies from case to case. To date, antiviral agents have no established place in the treatment of viral myocarditis. Where diagnosis is based upon endomyocardial biopsy (e.g., in lymphocytic myocarditis), immunosuppressive therapy generally has no significant effect.