Tissue pieces of small and large intestine from pre- and postnatal and adult rats, respectively, were transplanted to the anterior eye chamber of the rat. Immunohistochemical studies revealed high numbers of substance P-, vasoactive intestinal polypeptide (VIP)- and enkephalin-containing nerve fibers, especially in the circular smooth muscle layer and in the myenteric plexus of the intestinal tissue transplants. A small number of somatostatin-containing fibers were observed. The distribution patterns of the various peptide-containing neurons in the grafts resembled those which have been described in the intact gastro-intestinal wall. Substance P, VIP, enkephalin and somato-statin immunoreactive fibers were seen also in the host irides. No obvious differences in peptide innervation in grafts and host irides were observed between normal and sympathectomized animals and animals lesioned in the trigeminal ganglion. These findings suggest that most of the peptide-containing fibers in the intestinal transplants and the host irides originate in the transplanted tissue. Thus, it is shown that peptide neurons can survive in this transplantation model, which may be useful for functional studies of intestinal physiology including peptidergic mechanisms.