A 45 year old woman was admitted with New York Heart Association functional class III dyspnoea, with occasional orthopnoea and paroxysmal nocturnal dyspnoea. She was diagnosed as having rheumatic heart disease with severe mitral stenosis and atrial fibrillation. Echocardiography showed severe mitral stenosis, with a mitral valve area of 0.8 cm, mild mitral regurgitation, mild pulmonary hypertension, and good ventricular function. There were two echogenic structures with central translucency resembling the visual impression of rings in the left atrium. One was 3.2 cm × 2.9 cm lying close to the interatrial septum and was mobile, while the other was small and adhered to the posterior atrial wall. The mobile ring intermittently obstructed the mitral valve inflow, coinciding with the patient developing an episode of coughing. Our provisional diagnosis of organised clots was confirmed during surgery, following which the patient made a good recovery.