Many studies have addressed the relation between orthostatic hypotension (OH) and cognitive impairment (CI) in the elderly, in mild cognitive impairment, vascular and neurodegenerative dementias and movement disorders, such as Parkinson's disease. However, results concerning both the increased coexistence of the two conditions and their causal relationship remain controversial. According to the literature three hypotheses can be formulated on the relation between OH and CI. In neurodegenerative disease, OH and CI may result from a common pathological process which affects areas involved in both cognition and cardiovascular autonomic control. Alternatively, OH may lead to cerebral hypoperfusion which is supposed to play a role in the development of CI. Finally, recent data suggest that CI should probably be considered more a transient symptom of OH than a chronic effect. This study reviews the literature reports on the relationship between OH and CI, and emphasises the need for longitudinal studies designed to investigate this topic.