The invention features a catheter assembly and methods for delivering a hydrogel-lined stent to a body lumen, and methods for lining a stent with a hydrogel. The assembly includes a catheter which has a balloon at least a portion of which is coated with a hydrogel and an expansible stent mounted on the balloon in a contracted condition for passage with the catheter to a site of a body. Expansion of the balloon lodges the stent in the body with hydrogel coated on the inner surfaces of the stent as a lining.