Antihypertensive drug therapy is used in children primarily to treat secondary forms of hypertension, because the prevalence of essential hypertension in the first decade of life is considerably less than 1% of the childhood population. This prevalence increases during the second decade of life, but the percentage of teenagers with essential hypertension continues to be low. Pharmaceutical companies have been able to target drug development to specific physiologic and biochemical systems. The converting enzyme inhibitors and calcium-channel blockers have greatly improved the success of therapy concomitant with a reduction in the incidence of adverse effects. The result has been a major change during the past decade in the recommendations for antihypertensive drug therapy.