The results of this study, conducted in 25 patients without myocardial infarction, showed that all the biologic markers of myocardial infarction, except the highly cardiospecific cardiac troponin I, increased in some patients after electrical cardioversion. These results allow us to conclude that electrical cardioversion, even preceded by a mechanical resuscitation of short duration, does not result in myocardial damage, and that cardiac troponin I is more accurate than creatine kinase-MB activity and creatine kinase-MB mass determination for the diagnosis of myocardial damage in patients who have undergone electrical cardioversion.