A new reversibly gelling polyurethane (RGP) polymer composition is described, as well as novel processes for its preparation, and its medical uses for filling spaces in tissue, or bulking tissue, or for restoring organ function. The novel RGP polymer forms a gel on standing, liquefies during shear and reversibly reforms a macroscopic gel on standing after being sheared. Methods of use include delivering the improved gel to a site on the body to fill voids or to augment local tissue bulk.
