The left atrium, particularly the left atrial appendage (LAA), is prone to stasis and thrombosis; this is an especially important risk in patients with atrial fibrilliation and/or mitral stenosis. Transesophageal echocardiography remains the mainstay of left atrial imaging and thrombus assessment with excellent sensitivity and specificity. Spontaneous echo contrast or “smoke” is an independent risk factor for clot formation. LAA emptying velocity, as measured by pulse wave doppler, is often used as a surrogate of LAA ejection and correlated with the risk of stasis and thrombus formation. 3D evaluation of the LAA is more commonly deployed, particularly in the setting of catheter-based LAA occlusion devices. LAA thromboembolism is the leading cause of morbidity and mortality in atrial fibrillation, largely due to cardioembolic stroke.