The nucleus basalis of Meynert of the substantia innominata supplies the major cholinergic innervation of the cerebral cortex. Pathological alterations have been observed in the nucleus basalis of Meynert in several dementing neurological disorders. This paper is an overview of the work done by several researchers in their attempt to find the possible connections between pathology in the nucleus basalis of Meynert and the clinical symptomatology of dementia in several neurological diseases.