Background The abnormal blood volume regulation is one of the most important pathogenesis in postural tachycardia syndrome in children.This study was designed to investigate the plasma atrial natriuretic peptide and antidiuretic hormone levels in postural tachycardia syndrome children,and their associations with the changes in heart rate and blood pressure in head-up test.Methods Twenty-one postural tachycardia syndrome patients ((12±2) years) and 26 healthy children ((12±1) years) were included.According to blood pressure changes in head-up test,the postural tachycardia syndrome patients were divided into two subgroups:postural tachycardia syndrome with orthostatic hypertension and postural tachycardia syndrome without orthostatic hypertension.The plasma atrial natriuretic peptide and antidiuretic hormone levels were measured using enzyme-linked immunosorbent assay.Results The plasma atrial natriuretic peptide level in postural tachycardia syndrome patients was higher than the control (P=0.004),whereas the difference in plasma antidiuretic hormone level between postural tachycardia syndrome and controls was not significant (P=0.222).The plasma antidiuretic hormone level of patients suffering from postural tachycardia syndrome with orthostatic hypertension was much higher than that of children having postural tachycardia syndrome without orthostatic hypertension (P ＜0.05).In postural tachycardia syndrome patients,the updght max heart rate was positively correlated with the plasma atrial natriuretic peptide level (r=0.490,P＜0.05) and the upright systolic blood pressure was positively correlated with the plasma antidiuretic hormone levels (r=0.472,P ＜0.05).Conclusions There was a disturbance of plasma atrial natriuretic peptide and antidiuretic hormone in postural tachycardia syndrome children.