A stepped balloon catheter prosthesis deployment system is disclosed for placement of a prosthesis across an Os opening from a main body lumen to a branch body lumen. The balloon (212) has an inflated profile with a first section that is inflatable to a first diameter, and a second section which is inflatable to a second diameter which is larger than the first, and a balloon transition between the first and second sections. The prosthesis (210) carried by the balloon has a wall having a first wall pattern adjacent the first section of the balloon, and a second wall pattern adjacent the balloon transition.
