At the turn of the last century, infectious diseases represented an important cause of health morbidity and behavioral changes. Neurosyphilis, for example, was relatively common at the time and often led to the development of cognitive impairment and dementia. With the advent of effective antibiotic treatment, the association between infectious diseases and dementia became increasingly less frequent, although a resurgence of interest in this area has taken place during the past 15 years with the emergence of acquired immunodeficiency syndrome (AIDS) and variant Creutzfeldt–Jakob disease (vCJD). This paper reviews the most frequent infectious causes of dementia, including prion diseases, as well as infections caused by herpes virus, human immunodeficiency virus (HIV), toxoplasmosis, cryptococcus, cytomegalovirus, syphilis, borrelia and cysticercosis.