a method for producing a bioactive surface on an endoprosthesis , or on the balloon of a balloon catheter is described , wherein the surface of the endoprosthesis , or the surface of the balloon is softened . the surface of the endoprosthesis , or the surface of the balloon is moistened with a solution of an active ingredient , and the solvent is separated from the active ingredient . in addition , a balloon of a balloon catheter is disclosed , which comprises an uncoated surface , wherein an unencapsulated active ingredient is embedded at least partially into the material of the surface . furthermore , a balloon catheter is described , which comprises a balloon according to the invention . in addition , an endoprosthesis , particularly a polymer stent is described , which comprises an uncoated surface , wherein an active ingredient is embedded at least partially into the material of the surface .