Materials from our first autopsied case of diffuse Lewy body disease (DLBD), that was originally reported in 1976, were re-examined using recent immunohistochemical methods. Lewy pathology consisting of Lewy bodies and Lewy neurites appeared much more marked with alpha-synuclein immunostaining than had been detected with classical stainings. This case and our other similar cases prompted us to propose the terms “Lewy body disease” in 1980 and “diffuse Lewy body disease” in 1984. We also reported in 1990 that DLBD was classified into two forms: a pure form and a common form. Based on these studies the term “dementia with Lewy bodies (DLB)” was proposed in 1996. Since 1980, we have insisted that DLB, Parkinson disease (PD), and PD with dementia (PDD) should be understood within the spectrum of Lewy body disease. This insistence has been recently accepted by the International Workshop and the International Working Group on DLB and PDD in 2005 and in 2006, respectively.