The left atrial appendage (LAA) is an extension originating from the body of the left atrium. The LAA is derived from the primary atrium and shows anatomical and physiological deviations from the left atrium. Different LAA morphologies exist. The LAA is not only the most frequent origin of intracardiac thrombi, it also frequently shows triggers responsible for the initiation or maintenance of atrial tachyarrhythmia and atrial fibrillation (AF). Isolation of the LAA using radiofrequency energy in addition to isolation of the pulmonary vein has recently gained importance due to the potential for increasing the clinical success rates, particularly in patients with persistent and long-standing persistent AF; however, after LAA isolation the incidence of LAA thrombi and systemic thromboembolisms might be increased even under treatment with oral anticoagulants, depending on the ablation strategy used. Thus, mechanical occlusion of the LAA should be discussed with patients after electrical isolation of the LAA.