Congenital foramen of the left parietal pericardium is uncommon. The condition has the potential to cause angina pectoris, myocardial infarction, or even death. Forty-three confirmed cases have been retrieved from the English language literature, and a case report of "life-threatening" herniation of the heart is here added. The diagnosis, made at a mean age of 20 years (range 2 to 48), was five times more common in men. In 5 fatal cases, the heart had become incarcerated. In the remainder of cases, one-third were asymptomatic, and two-thirds suffered a chest complaint that prompted diagnosis. Chest discomfort, dyspnea, and syncope were the most common symptoms. The most common finding at surgery, which 34 patients underwent, was a foramen at the base of the heart through which the left atrial appendage had herniated. In eight instances, the rim of the defect lay upon and compressed the coronary circulation. Measures to remedy the disorder have included a variety of operations, some to enlarge the defect, others to close it, amputation of the atrial appendage, and, in two cases, myocardial revascularization. Surgery is appropriate in the majority of symptomatic patients and in all who are at risk for ventricular herniation.