1. In 70 patients with untreated essential hypertension, blood pressure variability was correlated to plasma catecholamines and to the response of blood pressure and peripheral flow to cold pressure and handgrip tests. 2. Supine blood pressure was recorded every 5 min, during 3 h. Variability was defined as the standard deviation of the mean of the readings in that period. 3. Blood pressure variability is positively and significantly correlated to the level of pressure and to age. 4. No significant correlation could be found with plasma catecholamines and sympathetic function tests. 5. It is concluded that blood pressure variability is related to the level of pressure but not to activity of the sympathetic nerves.