Fresh collagenous fibers from rabbit aponeurosis were prepared taking care to maintain their natural properties, and inserted into fascial tissue of the same animal. The tissue reactions were compared histologically to those produced by cotton, catgut and silk fibers similarly inserted in the same tissues. Around these fibers marked foreign body reactions were present. The reactions around the autograft fibers were minimal compared to those around cotton, catgut and silk. The possibility of using autograft fibers as sutures in certain surgical conditions and for operations in specific organs is suggested.