Twenty-two patients with hyperthyroid caxdiopathy(HTC),38 patients with hyperthyroid (HT),and 10 healthy controls were tested for plasma levels of brain natriuretic peptide(BNP).The findings showed that BNP level in HTC group(433±141)μg/L was significantly higher than that in HT group(110±38)μg/L and healthy control group(10±3)μg/L(both P<0.01);HT group vs healthy control group,P<0.01).After 3 months'treatment for HT,BNP decreased significantly.The patients with higher BNP levels had an increased incidence of HTC.Plasma BNP test might be useful in predicting the prognosis and the treatment efficacy in patients with HT.