Objective To investigate the relationship among the levels of B-type natriuretic peptide (BNP) and the extent,prognosis of acute aortic dissection (AAD).Methods The serum levels of BNP were measured in 42 AAD cases.According to the increasing level of BNP,the patients were divided into two groups:group A ( BNP≥ 500 ng/L,n =23 ) and group B ( BNP ＜ 500 ng/L,n =19 ).The extent of the disease and cardiovascular events were compared between the two groups.Results All the patients have elevated levels of BNP.The incidence of lasting aortic dissection (47.83％ vs.15.79％,P =0.048 ) and mortality ( 26.09％ vs.0,P =0.024) were higher in group A compared with those of group B.Conclusion The lasting and higher levels of BNP predict the increasing risk of bad prognosis in acute aortic dissection.