Objective To investigate the value and significance of the changes of plasma level of brain natriuretic peptide（BNP） in evaluating ventricle performance of functional single ventricle after total cavopulmonary connection （TCPC）. Methods We studied 11 patients with functional single ventricle undergone TCPC procedure after 2.1 years, who were followed-up at our ward between April 2004 and November 2004, 7 of them were males and 4 of them were females （TCPC group）. The clinical heart function of patients was scored according to the modified scoring system described by Ross. We obtained 3ml blood samples from the extremital vein of all subjects. Blood was collected into chilled tubes containing EDTA and aprotinin （4.5mg and 1 500u/ml blood, respectively）. The blood samples were promptly centrifuged （-4℃, 3 000r/min for 10 min） and the plasma was separated. BNP concentration was determined using immunoradiometric assay kits. Magnetic resonance imaging （MRI） examination was undertaken in 6 patients of TCPC group to analyse the relative factors with the change of BNP. Control group included 9 healthy children. Results （1） Median plasma BNP level for TCPC group and control group was 400pg/ ml （IQR200-690） and 110 pg/ml （IQR90-190）, respectively. There was a significant difference in plasma BNP between them （P=0. 003）. （2） The results of the index of heart function of TCPC group determined by MRI were 65. 76±8. 65 ml/m2 in end-diastolic volume index, 31. 90±6. 36ml/m2 in end-systolic volume index, 39.09±11.76ml/m2 in stroke volume index, 0. 52± 0. 06 in ejection fraction（EF）, 2.38±0.58L/min·m2 in cardiac index （CI）, 103.49±21.57g/m2 in mass index and 1.57±0.24 in mass/EDV. （3） The plasma BNP level for TCPC group was significant correlation with operation ages（r=0.632, P=0.041 ）. There was no correlation between plasma BNP level with EF, CI, score of Ross, gender, ages, percutaneous oxygen saturation（SpO2） and the type of dominant ventricle, respectively. Conclusions Raised concentration of plasma BNP in patients 2 years after undertaken TCPC procedure indicates that nervous-endosecretory system is still under stress condition. This pattern suggests that neurohormonal activation is primarily related to the altered postoperative physiology. the significance of BNP in patients of functional single ventricle after undertaken TCPC is different from tat in biventricular physiology patiens. The plasma BNP level could not be correctly evaluated the cardiac function after TCPC operation.