Since the enteric nervous system (ENS) has been demonstrated to display many similarities with the central nervous system (CNS), we have undertaken investigations examining the possibility of using the ENS as a source of neurons for transplantation into the brain in neurodegenerative diseases. Grafts of freshly dissected myenteric plexus taken from young inbred Fischer rats were implanted in the corpus striatum of adult Fischer rats, some of which had received a quinolinic acid lesion 1 to 2 weeks prior to implantation. Brain sections from the grafted animals were examined electron microscopically 3 and 6 weeks after implantation. Grafts contained many enteric neurons and glial cells in ganglia morphologically similar to those seen within the intestine. Although a glia limitans could be observed in parts of the interface between graft and brain, ganglia at the surface of the graft were observed to be closely apposed to the surrounding striatum, with no intervening basal lamina. CNS axonal sprouts were identified in the corpus striatum near the interface with the grafted enteric ganglia and bundles of similar axons, some containing fibers that had enlarged and become myelinated, could be seen within the grafts. A smaller number of CNS axonal sprouts were also observed around the grafts in the quinolinic-acid-lesioned striata. This study confirms that even in the absence of surrounding layers of smooth muscle, enteric ganglia grafted into the corpus striatum survive and stimulate the production of axonal sprouts from striatal and other neurons, which subsequently grow into the grafts.