Abstract Concentrations of neuropeptide Y (NPY) have been determined in 12 areas of control brains and compared to those found in brains from patients with Alzheimer's type dementia (ATD). The distribution of NPY in the control brains was compared with those reported previously. Highest concentrations were identified in the subcortical structures, in particular, nucleus accumbens (203 ± 21.7 pmol/g), amygdala (136.7 ± 15.8 pmol/g), and substantia innominata (109.0 ± 12.6 pmol/g). A significant elevation in NPY concentrations was identified in the region of the substantia innominata of Alzheimer brains (controls: 109.0 ± 12.6 pmol/g, ATD: 206 ± 28.2 pmol/g, P < 0.001). This change in NPY concentration was similar to the increase in somatostatin concentration in this region of ATD brain. In contrast, although cortical concentrations of somatostatin were reduced in ATD, no change was found in the concentrations of NPY in the 4 regions of cerebral cortex and the remaining subcortical areas examined.