BACKGROUND The question of whether to close the patent ductus arteriosus when performing primary modified Blalock-Taussig (MBT) shunt surgery in neonates is still not clearly answered. The aim of this report was to compare the results of closure versus nonclosure of the patent ductus arteriosus during MBT shunt surgery in neonates with pulmonary atresia. METHODS This retrospective study included neonates with pulmonary atresia who underwent primary MBT shunt surgery through a sternotomy approach at our institution between January 1997 and October 2010. Mortality, resuscitation events, and the need for reintervention within the first 48 postoperative hours were studied as primary outcomes. RESULTS Sixty-two neonates (mean age 6.9±5.5 days) underwent a MBT procedure. The arterial duct was closed surgically in 31 patients, and left open in 31 patients. Compared with patients in whom the PDA was left open, patients with a surgically closed arterial duct had a higher incidence of resuscitation events (29.0% versus 0%, p=0.0012), reinterventions (35.5% versus 3.2%, p=0.0013), and higher early hospital mortality (9.7% versus 0%, p=0.038). Time to extubation and length of hospital stay did not differ between the two groups (p=0.16 and p=0.73, respectively). A trend toward a higher maximum vasoactive-inotropic score in the group with a closed duct was observed (median 13.5 versus 10, p=0.10). CONCLUSIONS In newborns with pulmonary atresia, ductal closure during MBT shunt procedure is associated with increased incidence of resuscitation events, need for reintervention, and increased mortality during the early postoperative period.