Cardiovascular reflexes were analysed in a group of 20 patients suffering from Parkinson's disease and in 12 age-matched healthy subjects, in order to ascertain the incidence and degree of autonomic dysfunction. The following were measured: heart rate variation during normal breathing, postural change (30/15 ratio) and during the Valsalva manoeuvre: blood pressure variation after standing. These measurements were taken at least 12 h after therapy had been withdrawn and were repeated after therapy had been resumed. Significant changes in the different heart rate variation indices were found in the parkinsonian patients which correlated with the duration and severity of the extrapyramidal symptomatology. After standing the patients showed a significant drop in blood pressure, when compared respectively with their base values and with the response in controls. Anticholinergic drugs had no significant effect on the heart rate variation indices, whereas antiparkinsonian therapy seems to have contributed to the drop in blood pressure after standing.