OBJECTIVES: Atrioventricular septal (AVSDC) defect presents by excessive pulmonary blood fl ow and congestive heart failure in children. This study was designed to identify and compare N-terminal pro-brain natriuretic peptide (NT-proBNP) values in complete and incomplete form at the time of surgery, and evaluation of postoperative course. METHODS: The prospective study included thirty-one patients with complete and fi fteen with intermediate forms, undergoing surgery in the period from May 2009 to January 2014. Pre-and post-operative variables were statistically analyzed. RESULTS: The median value of NT-proBNP was 1420.0 pg/mL, with elevated levels in complete form (1656.0 vs 488.0 pg/mL, p < 0.001); age and weight with negative correlation. Other preoperative variables (genetic disorder, atrioventricular valve regurgitation, borderline ventricle) were not signifi cant. Higher incidence of postoperative variables was present in complete form, namely mechanical ventilation (p < 0.03), dose and length of vasopressors (p < 0.002), ICU stay (p < 0.04), and complications (p < 0.05). NT-proBNP analysis as a predictor of postoperative course showed an association with longer ventilatory (> 48 hours) and inotropic forms of support, ICU stay, and presence of infection. CONCLUSION: NT-proBNP value might be helpful in the decision-making process of early surgical treatment of complete form of AVSDC, and useful as a predictor of early post-operative course (Tab. 4, Fig. 3, Ref. 14). Text in PDF www.elis.sk. KEY WORDS: NT-proBNP, atrioventricular septal defect, congestive heart failure, postoperative course. Acknowledgements: We would like to acknowledge the cooperation of the colleagues in the operating room and biochemical laboratory of our institution.