In recent years, a new cardiac syndrome with transient left ventricular dysfunction has been widely reported in Japan. This new entity has been referred to as "tako-tsubo cardiomyopathy" or "apical ballooning", named for the particular shape of the end-systolic left ventricle in ventriculography. This syndrome has also been reported to occur in the western population. The clinical characteristics of this phenomenon have been described as follows: (1) acute onset of reversible left ventricular apical wall motion abnormalities (ballooning) with chest pain, (2) electrocardiographic changes (i.e., ST elevation), (3) minimal myocardial enzymatic release, and (4) no significant stenosis on coronary angiography. Severe emotional or physical stress usually precedes this cardiomyopathy. A unifying mechanistic explanation responsible for this acute but rapidly reversible contractile dysfunction is still lacking. Several investigations suggested catecholamine-mediated cardiotoxicity or coronary artery vasospasm, microvascular injury, an impaired fatty acid metabolism, or transient obstruction of the left ventricular outflow. The optimal treatment of patients presenting with this syndrome may depend on the stage of condition, since various pathophysiological mechanisms underlie the final clinical picture.