AbstractThe precise role of the nerve growth factor protein (NGF) during the growth and development of the human nervous system is not determined. Although it appears to influence a number of neural functions, its mechanism of action is poorly understood. A number of researchers have proposed that NGF may be involved in several pathological conditions including cancer. It has been shown that NGF is secreted'by certain sarcoma (23), neuroblastoma (113), and glioma (7,102,136) cell lines and can bind to neuroblastoma and metastatic melanoma cell lines (42). Neuroblastoma (136,181) and pheochromocytoma (165) cells in vitro can be induced by NGF to differentiate toward a morphologically “more benign” state and appropriate NGF treatment of rats can reduce the number of chemically induced gliomas and neurinomas (174, 178). NGF can also reduce the growth of intracerebrally inoculated anaplastic glioma cells (172). Anti‐NGF treatment of rats (178) and mice (179) can alter the tumor distribution observed following ethylnitrosourea or benzo(a)pyrene treatment (10). In humans, it has been reported that serum levels of NGF are usually elevated in persons “at risk” for neurofibromatosis (156). The precise nature of the NGF role is not known in these instances. Further understanding of the action of NGF could be of clinical i