1. In the present study, we measured the concentrations of 5-hydroxytryptamine (5-HT), norepinephrine and dopamine in post-mortem brains from five patients with diffuse Lewy body disease (DLBD), in comparison with five brains from patients with Alzheimertype dementia (ATD), and five brains from normal controls. 2. They were measured by means of high-performance liquid chromatography fluorometric detection. 3. Compared with the ATD and normal control brains, the DLBD ones showed decreased concentrations of 5-HT, norepinephrine and dopamine in the putamen, and lower 5-HT and norepinephrine concentrations, and almost equal dopamine ones in the neocortex.