Eight further cases of neurogenic orthostatic hypotension are described together with a necropsy study on one case. Three cases showed evidence of autonomic dysfunction in isolation, while in five cases this was accompanied by evidence of more diffuse central nervous system degeneration. (Parkinsonism, cerebellar ataxia, dementia, pyramidal signs, bulbar weakness, and muscular wasting were all seen in varying proportions.)The various clinical presentations, investigations, pathology, treatment, and prognosis are discussed. In the experience of the authors, when assessed, an abnormal Valsalva response is invariable, confirming the breakdown of the circulatory reflex. A normal vasopressor response is likewise invariable, eliminating an abnormality of blood vessels themselves, and confirming the lesion as neurogenic. The demonstration of loss of sweating to indirect body heating, which also is usual suggests that the defect is central or on the efferent side of the reflex and a normal pilo-erector response to acetylcholine confirms this as preganglionic. Emphasis is laid on the non-specificity of many accepted physiological tests in this disorder and on the delay in diagnosis consequent upon the variable presentation.