A stent (2) for insertion in a fluid conduit of the human or animal body when the stent is in a collapsed condition and for expansion to an expanded condition, the stent comprising an outer wall(7) for engagement with the conduit, the outer wall having a helical portion (6) which in the expanded condition extends longitudinally and circumferentially, and which, upon expansion of the stent from the collapsed condition to the expanded condition, resists extension.
