Contrary to what the name implies, the left atrial appendage is increasingly becoming an organ of clinical importance. Its role in the pathogenesis of thromboembolism is now well established. Enlargement of the appendage due to haemodynamic disturbances or anatomic weakness increases this risk, along with the potential for arrhythmia. We report a rare case of gross enlargement of the left atrial appendage within the pericardial cavity.