The purpose of this study was to evaluate the safety and the efficacy of transcatheter patent ductus arteriosus (PDA) occlusion with the Duct-Occlud device. Six centers participated in this phase I U.S. Food and Drug Administration-approved clinical trial with investigational device exemption. Patients with restrictive PDA (less than 4-mm minimum diameter) were eligible for the study. Sixty-two patients were enrolled. Forty-eight patients had successful implantation of Duct-Occlud devices. Patient follow-up evaluations were conducted at hospital discharge and after 2 and 12 months. At discharge and after 1 year, all patients had clinical PDA closure. Closure assessed by color flow Doppler was 55% at discharge, 88% at 2 months, and 94% at 1 year. There were no complications related to implantation or noted in follow-up evaluations. The Duct-Occlud device is safe and efficacious for the closure of small- to moderate-size patent ductus arteriosus.