1. After 10 years of β-adrenoceptor blockade in five female patients with essential hypertension, the β-adrenoceptor-blocking agent was withdrawn, and the women were then followed up for 1 year, with measurements of cardiac output and peripheral resistance.
2. Blood pressure remained low during the first year after withdrawal in spite of the fact that the heart rate increased within the first few days.
3. Cardiac output was found to increase during the first year after withdrawal, although total peripheral resistance was essentially unchanged.
4. The maintenance of low blood pressure after withdrawal of the antihypertensive drug might indicate a regression of structural changes in the resistance vessels during successful long-term antihypertensive treatment.
5. Minimal resistance in hands and calves did not increase during the year after withdrawal.