The high cardiac output state and an increased incidence of atrial fibrillation are well-known cardiovascular complications of Graves' disease, whereas the valvular complications are less well recognized. With 2D color Doppler echocardiography, the cardiac and valvular function of 39 patients with Graves' disease were evaluated and our data were compared with previous Kage's study. The incidences of mitral regurgitation (MR) and tricuspid regurgitation (TR) in patients with Graves' disease were 54% and 51%, respectively. There was no correlation between the incidence of MR and ventricular dilatation. In patients with congestive heart failure (CHF), the incidences of severe TR and atrial fibrillation were significantly higher than in patients without CHF. The incidences of TR and MR in patients with Graves' disease were not different by thyroid function status (hyperthyroid vs. euthyroid). We suggest that the examination for TR and MR in patients with Graves' disease is important not only their high prevalence but also their clinical significance as a risk factor for CHF.