Abstract: A system and apparatus are disclosed for preparing tubular prostheses from a sheet of tissue and inner and outer helical frame components. The tissue is wrapped around the inner frame component over an assembly mandrel. The outer helical frame component is then transferred from an elongate support over a lead screw, onto the assembly mandrel by rotating the assembly mandrel and lead screw in a manner which positions the outer helical frame component in an appropriate manner. Optionally, the mandrel is collapsed to facilitate removal of the completed tubular prosthesis.