Nerve growth factor (NGF) was injected into the lateral ventricle (5 micrograms on 4 occasions) of rats which had previously sustained ibotenic acid-induced lesions of the nucleus basalis of Meynert. Lesioned, but vehicle-injected and sham-lesioned and vehicle-injected rats were run as controls. Infusion of NGF led to a significant recovery of cortical choline acetyltransferase and acetylcholinesterase activity 6 weeks, but not two weeks after the lesion.