The paper reports the results of recordings and maps of event-related potentials (ERPs) in patients with Alzheimer's disease (AD), progressive supranuclear palsy (PSP) and in subjects affected by dementia in multiple sclerosis (MS). ERPs were recorded from 19 scalp electrode derivations using both visual and acoustic paradigms. In 43% of AD patients, ERPs were normal; in 20%, although present, ERP components were delayed, while in the other 37% none of the N2 and P3 peaks could be recorded, because of abnormal topography of potentials on the scalp. In patients with PSP, the normal ERP sequence was not identified. In patients with MS delayed ERPs (50%), abnormal topography of ERPs (30%) and absence of ERPs (20%) were observed. The follow-up of AD patients showed a progressive alteration of ERPs. ERP topography alterations were observed in AD, PSP and MS patients with poorest cognitive performances.