Methods and apparatus are provided for forming a vascular graft in vitro by axially distending a blood vessel to induce growth. The apparatus comprises a chamber containing a tissue culture medium, an inlet cannula, an outlet cannula, and a means for moving the inlet cannula, the outlet cannula, or both, to axially stretch a donor blood vessel secured between the inlet cannula and the outlet cannula in a submerged position in the tissue culture medium, wherein the inlet cannula, the outlet cannula, and the donor blood vessel are secured together to form a conduit through which the tissue culture medium can flow.