Experimental venous pouch aneurysms in rats were wrapped with muscle, bovine collagen, muslin, cotton, or polyvinyl alcohol. The rats were killed 6 or 12 weeks later, and the aneurysms were compared with control aneurysms. Bovine collagen and muscle were reabsorbed and the aneurysms were similar to the control group. Cotton, muslin, and polyvinyl alcohol caused fibrosis around the aneurysm. However, giant aneurysms were found in the muslin and polyvinyl alcohol group. Cotton appears to be the most suitable material for wrapping aneurysms. The experimental venous pouch aneurysm model in rats can be used to evaluate wrapping materials.