The topographical distribution of the choline acetyltransferase (ChAT) activity and the number of muscarinic binding sites was studied in the anterio-posterior direction of the caudate nucleus, hippocampus, globus pallidus and putamen of four subjects with senile dementia of Alzheimer type (AD/SDAT) and in the same regions in six controls. Intranuclear gradients were observed both for ChAT and muscarinic receptors. The data obtained were compared with data on noradrenaline (NA) concentration. With longer duration of the disease a decrease was found in the noradrenergic and cholinergic systems. One patient died acutely after a rather short duration of the disease. In this patient no change in ChAT activity was found while the NA concentration was decreased in all brain regions. An upregulation of the number of muscarinic receptors was observed in the caudate nucleus and putamen of all cases, except for the case with the shortest duration of the disease.