A mitral valve annuloplasty prosthesis (ring or C) has a generally saddle shape, i.e., portions of the prosthesis that are or will be adjacent the anterior and posterior commissures of the valve are relatively low as compared to at least some other portions of the prosthesis that are or will be between the commissures. However, the saddle shape is asymmetrical, in that the portion that is or will be adjacent the posterior commissure is lower than the portion that is or will be adjacent the anterior commissure.