Immunization with purified cardiac myosin induces autoimmune myocarditis in A strain mice. Because this disease parallels Coxsackievirus B3 (CB3)-induced myocarditis in many respects, we are now using the immunization model as a virus-free system to study certain forms of immunologically-mediated heart disease. In the present article we will describe several characteristics of the humoral and cellular autoimmune response acting in myosin-induced myocarditis. Furthermore, we discuss hypotheses which might explain how myosin-reactive T cells recognize and attack the heart tissue.