Orthostatic hypotension (OH) is defined as a fall in blood pressure of at least 20 mmHg systolic or 10 mmHg diastolic when standing or during head-up tilt testing. The prevalence of OH increases with age, with disorders that affect autonomic nerve transmission, and with increasingly severe orthostatic stress. In normal elderly subjects, the prevalence of OH is reported to be between 5 and 30%. The actual prevalence depends on the conditions during diagnostic testing, such as the frequency of blood pressure recordings, the time of day and the degree of orthostatic stress. Elderly subjects are often taking medications, such as antihypertensives and diuretics that can cause or aggravate OH. Neurological diseases such as diabetic neuropathy, Parkinson's disease, multiple system atrophy and the autonomic neuropathies further increase the likelihood of OH. The development of OH in normal subjects is associated with an increased mortality rate. OH in diabetes is also associated with a significant increase in mortality rate.