A tubular prosthesis, which may be an endovascular prothesis, is provided which includes a tubular member (stent or stent/graft combination) and an outer covering having portions sealed to the tubular member. The tubular member is impervious to a pre-determined fluid, particularly an occluding fluid, while the outer cover is pervious to the pre-determined fluid. In one aspect of the present invention, the implantation of the prosthesis allows for occluding fluid to weep from the prosthesis and into a sac of an aneurysm to cause occlusion thereof without introducing the occluding fluid into the blood stream. In this manner, a Type II failure of the prosthesis may be avoided. In other aspects of the invention, therapeutic agents may be delivered and/or a seal may be formed about the prosthesis to prevent a Type I failure.