This article discusses the efficacy, use and adverse effects of antihypertensive drug therapy in older adults. Numerous double-blind, randomized, placebo-controlled studies have demonstrated that antihypertensive drug therapy reduces cardiovascular events in older adults. All antihypertensive drugs may predispose older patients to the development of symptomatic orthostatic hypotension and postprandial hypotension, and syncope or falls. Adverse effects of diuretics, beta-adrenergic receptor antagonists, ACE inhibitors, angiotensin receptor antagonists, calcium channel antagonists, alpha-adrenergic receptor antagonists, centrally acting drugs and direct vasodilators are discussed. The adverse effects depend on the antihypertensive drugs used, the doses used, the co-morbidities present in older patients taking these drugs and drug-drug interactions.