A preliminary experiment was devised to delineate the specificity of nerve allograft rejection. Skin grafts were performed between inbred strains of Fisher, AgB1, and Buffalo, AgB6, rats to determine the time required for a first set rejection, which occurred at day 9. Skin grafts also were performed two weeks after orthotopic placement of whole nerve or fascicular grafts. The rats that had previously been exposed to whole nerve showed skin graft rejection at six days, while those exposed to nerve fascicle demonstrated skin graft rejection at seven days. Fascicular whole nerve allografts and autografts were compared histologically at seven, 12, 19 and 28 days after grafting. The whole nerve allograft consistently showed gross and microscopic evidence of lymphocytic infiltration consistent with rejection involving the perineural connective tissues. Antigens obviously are present in sufficient levels in both the nerve and surrounding connective tissue, but at least, theoretically, there are some advantages to the use of fascicles versus the whole nerve.