Objective:To investigate the changes in plasma ET-1 and ANF in IDDM and its microvascular complication.Methods:The plasma levels of ET-1 and ANF were measured by radioimmunoassy in 31 patients with IDDM and 25 normal controls.Results:The plasma levels of ET-1 and ANF significantly increased in IDDM compared with the normal controls (P<0.01);and the levels were also markedly higher in diabetics with microangiopathy complications than in those withou the complications (P<0.01).The more kinds of microangiopathey complications,the higher level of the plasma ET-1 and ANF,which suggests that the elevation of plasma ET-1 and ANF may be concerned with the microangiopathy and ET-1 may reflect the degree of vascular endothelial cell damage.There were no significant correlation between plasma ET-1 or ANF and blood glucose,fructosamine and C-peptide,but the plasma levels of ET-1 and ANF both correlated with the duration of diabetes mellitus.And the plasma level of ET-1 positively correlated with ANF1 (P<0.01).Conclusion:The results of study suggest that ET-1 and ANF are both associated with the development,progress and severity of microvascular complications.