Experimental neurosurgical implantation of adrenal medulla tissue has been performed as a treatment for Parkinson's disease at several medical centers around the world, and similar techniques have been applied in a small number of nonhuman primates. None of these efforts to date has resulted in histological evidence of significant graft survival, and behavioral improvement in patients has been modest at best. The present series of experiments, however, has led to a novel and effective technique for stereotaxic implantation of long, narrow "ribbons" of autologous adrenal tissue in the monkey caudate and putamen nuclei. The survival and enzymatic activity of large portions of intact grafted ribbons have been demonstrated by tyrosine hydroxylase immunohistochemistry. Efforts based on other grafting techniques resulted in poor or mediocre survival, reminiscent of previously published results. Successful grafts, on the contrary, were morphologically similar to intact adrenal medulla tissue, except that neuronal processes were observed emanating from some of the transplanted cells. The success of the present technique, which minimally distorts or traumatizes adrenal and brain tissue, may be due primarily to the rapid establishment of a blood supply by anastomosis with host vessels. In most monkeys, nerve growth factor was also administered to the lateral ventricle for the duration of the graft, but excellent results were also achieved in the monkey that did not receive such treatment. We conclude that adrenal grafts made by the present technique can survive and function in primates.