Ischemia-modified albumin (IMA), measured with the albumin cobalt binding test, is a marker of myocardial ischemia. We measured IMA concentrations after elective direct-current cardioversion for atrial fibrillation to determine whether transient myocardial ischemia occurs. Patients with electrocardiographic changes after cardioversion (ST-depression and/or T-wave inversion) had significantly higher IMA levels than those without these changes. Thus, elevated levels of IMA after cardioversion may reflect transient myocardial ischemia.