Objectives: This study assessed the feasibility and efficacy of implanting a new miniaturized nitinol device to occlude the patent ductus arteriosus (PDA) in a newborn porcine model. Background: Transcatheter device closure is the standard of care for PDA in older children and adults. Currently available technology is not designed for the newborn infant. Methods: The Amplatzer Duct Occluder II 0.5 is a new transcatheter Nitinol device without fabric designed to close the PDA with small aortic and pulmonary artery structures. The device was implanted in 8 infant pigs (average weight 2,400 g) after balloon dilation of PDA (average diameter 2.7 mm, average length 5.8 mm) with immediate, ∼ 7, ∼ 30, and ∼ 90 day follow-up by echocardiography, angiography, and final pathological examination. Half were implanted arterial, and half venous. Results: The device was successfully implanted in all animals. There was complete occlusion of the PDA in all cases without obstruction of the pulmonary arteries or aorta. There was complete late endothelialization without thrombus. The only complication was transection of a femoral artery accessed by cutdown. Conclusions: The success of this animal study confirms safety and feasibility of the Amplatzer Duct Occluder II 0.5 (now known as the ADO II AS) for use when the aorta and pulmonary arteries are small. Consideration can be given to transcatheter closure of the PDA in preterm and other small infants with this device. © 2011 Wiley Periodicals, Inc.