The frequency of myocarditis and the prognosis for patients remains uncertain and, moreover, the clinical classification of myocarditis is controversial. From 1985 to 2000, 71 adult patients with clinically suspected myocarditis were admitted to 11 cardiovascular centers. Of these, 48 cases had histology proven myocarditis: 41 cases of lymphocytic myocarditis, 6 of giant cell myocarditis and 1 of eosinophilic myocarditis. Myocarditis was classified as acute (30 cases) or chronic (18 cases) according to the onset of the disease, and acute myocarditis was further categorized into common or fulminant type depending on whether or not patients required mechanical circulatory support in the management of heart failure (9 and 21 cases, respectively). Chronic myocarditis was divided into 3 subgroups: a persistent type lasting over 3 months after distinct onset (3 cases), a recurrent type (2 cases) and a latent form (13 cases). The early mortality of these 5 subtypes of myocarditis were acute common 22%, acute fluminant 43%, chronic persistent 33%, chronic recurrent 50%, and chronic latent 38%. The overall early mortality of all patients with myocarditis was 38% in spite of aggressive treatment during hospitalization. On the other hand, the long-term prognosis of patients with myocarditis was favorable; only 4 cases, who survived the active phase, died in the late phase: 1 had fulminant myocarditis and the other 3 had the chronic latent form. Thus, the early mortality of patients with myocarditis was very high regardless of the subtype, but if patients can survive the active phase, they have a favorable prognosis except with the chronic latent form.