Abstract: Objective To study the preventive effects of nerve growth factor(NGF)on basal forebrain neurons to explore the therapy for Alzheimer disease.Methods Six aged Rhesus monkeys were divided into two groups(group A and group B)randomly.NGF transport from cerebral cortex were blocked in all the monkeys.Group A received homopleural intraventricular implants of polymer-encapsulated cells that were modified to secrete NGF.Group B received identical implants of empty capsules.Results Three to four weeks after operation,the monkeys in the group B displayed extensive reductions in the number of p75NGFr receptor immunoreactive neurons(53%)and choline acetyltransferase immunoreactive neurons (57%to 75%)within the septum.The monkeys in group A appeared to be normal size telative to the atrophic appearance of cholinergic neurons and p75NGFr receptor imrnunoreactive neurons in the monkeys receiving control implants.Conclusion NGF could prevent basal forebrain neuron degeneration in aged monkeys.