Devices and methods are provided for forming a vascular graft by axially distending a blood vessel to induce growth. The device preferably comprises a stretching mechanism which includes (i) a stabilization rod, (ii) a pair of rotatable elements, wherein each rotatable element is rotatably attached to the elongated body and has a channel substantially perpendicular to the axis of rotation, and (iii) a means for rotating each rotatable element to axially distend a blood vessel positioned in the channels of the rotatable elements. The elements can be rotated intermittently, cyclically, or continuously, over a period to distend or elongate the donor vessel. Preferably, the device is implanted, for example using endoscopic techniques, for use in vivo, although the device also can be used in vitro.