1. Deoxycorticosterone acetate (DOCA) implantation (100 mg/kg) caused mean arterial pressure to rise in 5–10 days from control pressures of 100–115 mmHg to stable hypertensive valnes of 140–160 mmHg in approximately 1 month. In six of seven pigs elevations of mean arterial pressure were entirely the result of increased total peripheral resistance. 2. Single implants maintained serum DOCA at approximately ten times normal concentration for up to 90 days. 3. Moderate but variable decreases in serum aldosterone followed implantation. 4. Hypokalaemia, polydipsia and suppressed plasma renin activity were evident by the fifth post-implantation day and persisted thereafter. No consistent change occurred in serum sodium. 5. Noradrenaline or angiotensin caused increases in total peripheral resistance at lower threshold infusion rates in hypertensive pigs compared with control animals. 6. In isolated, perfused hind-limb preparations, hypertensive vascular beds were characterized by both functional (increased vascular smooth muscle sensitivity) and structural (elevated resistance of maximally dilated vascular bed) changes. ‘Protection’ from increased arterial wall stresses in hypertensive pigs prevented structural, but not functional, alterations.