With two-dimensional (2D) color Doppler echocardiography, the cardiac and valvular function of 24 consecutive patients with a history of Graves' disease (17 were hyperthyroid and 7 were euthyroid at the time of the examination) were evaluated. The incidences of mitral regurgitation (MR), tricuspid regurgitation (TR) and MR plus TR were significantly higher in the patients with Graves' disease than in the age-matched control group of patients without this disease. In the patients who had signs of congestive heart failure (CHF) while they were hyperthyroid, a significantly higher incidence of severe TR was observed. This is the first report of a 2D color Doppler echocardiography study on the incidences of TR and/or MR in patients with Graves' disease. Our data indicate that in Graves' disease valvular dysfunction can be caused by systemic disorders and that severe TR is a possible risk factor for CHF.