OBJECTIVE: To evaluate the biocompatibility of the home made atrial septal defect (ASD) occluder device. METHODS: ASD animal models with different size defects were established by the brockenborough needle followed by Rashkind balloon atrial septostomy. Occluder devices were implanted in six piglets (mean weight 7.5 kg ). Two pigs were sacrificed after 1 month, 3 months and 6 months of implantation respectively. Macroscopic and microscopic assessments were done on the explanted devices. RESULTS: Macroscopic examination showed no excrescence, thrombus formation, arm fractures and corrosion. The devices were mostly embedded in soft tissues three months after implantation and embedded completely by 6 months. Microscopic examination showed apparent inflammatory infiltration inside and around the devices; the devices were covered with collagen fibrin and diffuse endothelial cells 1 month after implantation. By 3 months after implantation, fibrosis was formed while the inflammatory reaction decreased gradually; myocardial cells ingrowed at the edge of the devices; endothelium like cells could be found on the surface of the devices. By 6 months after implantation, neovascularization and lymphatic vessel ingrowth were noted; the inflammatory reaction diminished with only a few chronic inflammatory cells; the devices were completely covered by endothelium and fibrous tissues. CONCLUSIONS: The home made ASD occluder device has a good biocompatibility.