This overview examines the immunological rationale for immunosuppressive and immunomodulating therapy in man and experimental animals. The controversy of whether immunosuppressive treatment is beneficial in myocarditis will continue even after the Myocarditis Treatment Trials has been published. It is known that in viral heart disease immunosuppressive drugs should be avoided, but in autoreactive forms of myocarditis with proven humoral and cellular effector mechanisms they may be used in controlled randomized trials to validate or refute their benefit. Immunomodulating factors, e.g. immunostimulatory or antiviral substances such as ribaverin, the interleukins and interferons have demonstrated some effect in experimental animal myocarditis but proof of their benefit in man is still lacking. Hyperimmunoglobulin therapy appears to be of particular interest because it incurs few side effects and has positive results in cytomegalovirus-associated myopericarditis in man and suspected myocarditis in children.