Nearly every fifth mitral stenosis presents thrombi in the left atrium and therefore has remarkable therapeutic consequences. Most thrombi are located in the left atrial appendage, but atrial appendage thrombus can also extend to the left atrial cavity as in the presented case. This case shows the advantage of a combined diagnostic by MRI and transoesophageal echocardiography for a fast and sufficient detection as well as topologic classification of left atrial thrombi.