A method of making an internal bidirectional branch and an endoluminal prosthesis from a tubular segment of graft material. The tubular segment is partitioned into first and second sections along a length of the tubular segment. The first section has a width less than a width of the tubular segment, and the second section has a width less than the first section. The second section is partitioned into at least three sub-sections. The tubular segment is connected along a lateral edge of the first and third sub-sections of the second section. The tubular segment is turned inside out such that the bidirectional branch is positioned within a lumen of the first section and an opening of the second sub-section is exposed.