Abstract This study was undertaken to determine the long-term performance of a two-ply biodegradable, compliant microarterial prosthesis for its ability to function successfully as a temporary scaffold for the regeneration of a neoartery. Two-ply microarterial prostheses (internal diameter 1.5 mm, length 1 cm), prepared from a polyurethane-based (PU) material, were implanted into the abdominal aorta of rats (n = 22) and were evaluated at 3 months (n = 6), 6 months (n = 6) and one year (n = 10) after implantation, by means of macroscopic inspection, light microscopy and electron microscopy. All implants were patent and all, except two with a very small local dilatation at one year, were normally shaped. Arterial pulsations were reduced but still visible in all implants. In all implants a neoartery had regenerated: (1) a complete neointima composed of endothelial cells, (2) a neomedia composed of smooth muscle cells surrounded with elastin and collagen and of comparable thickness to rat media, and (3) a neoadventitia composed of fibrohistiocytic tissue that had organised the graft wall. In 2 out of the 10 one-year implants, smooth muscle cells were predominantly circularly arranged as in normal arterial tissue; in all other implants smooth muscle cells were predominantly longitudinally arranged. These results demonstrate that two-ply biodegradable PU-based prostheses have a good long-term performance when implanted into rat abdominal aortas.