A tubular graft/stent includes a tubular sheath (10) having at intervals along its length a plurality of ring-like rigid members (11), which are attached to the sheath around their respective circumferences and are made of a shape memory material, so that when the members (11) change shape the sheath (10) adopts a new cross section in conformity with them along its whole length. The members may be discontinuous to allow the adoption of a contracted shape in the martensitic phase and an expanded shape in the austenitic phase. A graft may also have a side tube (14) which can be inverted so as to be housed within the sheath.