SummaryThe authors report a case of myocarditis associated with mycoplasma pneumoniae in a 43 year old man. A rise in complement-fixation antibody titers between acute and convalescent phase sera indicated infection by mycoplasma pneumoniae. The clinical symptoms mimicked a myocardial infarction or a pulmonary embolisml The electrocardiogram showed important changes, with right bundle branch block, signs of myocardial infarction and sub-epicardial ischemia in the antero-septal region. Recovery was complete after 10 days of erythromycin treatment.