The immunohistochemical localization of nerve growth factor receptor (NGFR)-high-affinity NGFR (trk A) and low-affinity NGFR (LNGFR)-was investigated in 23 neuroblastoma group tumors, 18 pheochromocytomas, 2 mixed neuroendocrine-neural tumors, and 16 retinoblastomas. trk A was expressed in the tumor cells of all neuroblastomas, pheochromocytomas, and retinoblastomas. Immunoreactive intensity was especially strong in the larger ganglionic tumor cells of ganglioneuroblastoma and ganglioneuroma. Messenger RNA (mRNA) of trk A was also strongly expressed in the ganglionic cells of ganglioneuroblastomas and chromaffin cells of pheochromocytomas by in situ hybridization method. LNGFR was negative in the tumor cells of neuroblastoma; however, it showed strong immunoreactivity in ganglionic tumor cells and Schwann cells of ganglioneuroblastoma/ganglioneuroma, and sustentacular cells of pheochromocytoma. Although normal retina expressed both trk A and LNG FR, tumor cells of retinoblastoma were positive for only trk A but negative for LNGFR. Such differences in the expression of trk A and LNGFR may reflect neuronglial interactions in the survival and maturation of the sympathetic nerves, retina, and tumors in these tissues.