Calcium antagonists and converting enzyme inhibitors are now widely used as first line therapy for high blood pressure. This gradual move from the diuretics and beta-blockers is, in part, due to fewer or different side effects and the perceived lack of deleterious metabolic effects. Calcium antagonists may be more effective in elderly and low-renin patients. However, this is likely to be due in part to the finding that calcium antagonists are more effective with a higher initial pressure. The efficacy of converting enzyme inhibitors is related to the initial level of plasma angiotensin II (Ang II) or plasma renin activity. However, patients with low plasma renin activity also have a fall in blood pressure with converting enzyme inhibitors, illustrating the importance of differences in Ang II receptor sensitivity to the prevailing level of Ang II. Many patients require the combination of more than one drug to control their blood pressure. Combining a converting enzyme inhibitor with either a dihydropyridine or a benzothiazepine calcium antagonist is a particularly effective approach to the treatment of patients with more severe essential hypertension.