1. Cardiovascular reflex activity has been studied in thirty Parkinsonian patients, none of who had received levodopa or sympatholytic drugs.
2. Changes in blood pressure and pulse rate in response to Valsalva's manoeuvre and head-up tilt were investigated by intra-arterial recording.
3. Cardiovascular reflex function deteriorated with advancing age, but there was no correlation with either the duration or the severity of the Parkinsonism.
4. These results are discussed in relation to previous reports of hypotension in Parkinsonism.