Cardiac tamponade following open heart surgery is well described, although, fortunately, uncommon. Unlike more classical "primary" tamponade, the clinical features are not specific, and this can delay diagnosis. In practice, the threshold for investigation must be low, and echocardiography has been invaluable in the detection and localization of pericardial collections. Several factors are believed to contribute to the likelihood of postoperative tamponade, but the mechanisms are not clearly understood. Resternotomy, under general anesthesia, or subxiphoid pericardiotomy, under local or general anesthesia, are effective forms of treatment. However, recent success with the use of percutaneous pericardiocentesis under echocardiographic guidance has shown that postoperative tamponade can be treated safely and effectively by this method.