A fastening system for an electrical stimulation generator, with a generator and an electrode, has a casing for containing the generator that presents identical first and second openings, disposed on opposite sides; means for the connection of the electrode to the first or second opening in the casing formed by a first pass-through connector for the electrode, with a sealing element; an airtight closing element disposed at the opening of the casing opposite the one presenting the means for the connection of the electrode; a device for securing the electrode to the skin; and means for fastening the casing to the body of the patient.