1. Circulatory reflex function was assessed in a series of subjects with chronic ischaemic cerebrovascular disease and compared with a group of subjects with no known cerebrovascular disease by intra-arterial pressure responses to Valsalva's manoeuvre.
2. Circulatory reflexes were impaired in the patients with cerebrovascular disease as compared with controls, but statistical analysis indicated that age was a more important factor than chronic cerebrovascular disease in producing the deterioration.
3. No significant difference was found in the circulatory reflex function of subjects with ischaemia in the internal carotid territory when compared with those having ischaemia in the vertebrobasilar territory.
4. Combined ischaemia in both carotid and vertebrobasilar territories significantly impaired the cardioaccelerator but not the vasoconstrictor response to Valsalva's manoeuvre.
5. No significant difference was found in circulatory reflex function in subjects who had suffered cerebral infarction as opposed to transient ischaemic attacks.