Basal forebrain neuronal atrophy in Alzheimer's disease (AD) may be caused by a deficit in the NGF responsiveness of magnocellular cholinergic neurons which project to the cerebral cortex and hippocampal formation. We have used in situ hybridization to show that NGF-receptor (NGF-R) mRNA-positive neurons are lost within all divisions of the nucleus basalis of Meynert (Ch4 cell group) in AD patients as compared to normal aged controls. The posterior division of the nucleus basalis showed the largest decrease in NGF-R mRNA hybridization in the disease, with no overlap in neuronal number between AD cases and normal controls. Northern (RNA) blotting showed decreased levels of NGF-R mRNA in the nucleus basalis in the disease. No differences in the number of NGF-R mRNA-positive neurons between normal aged and AD patients were detected within the NGF-responsive cell groups of the medial septum (Ch1) and nucleus of the vertical limb of the diagonal band (Ch2). These results show that NGF-R gene expression is selectively reduced within basal forebrain neuronal populations which exhibit degenerative changes in AD.