Individuals with hypertension need to stay on therapy with antihypertensive medication to obtain the full benefits of blood pressure reduction. There are important differences in tolerability across antihypertensive drug classes, and these differences influence the extent to which patients are willing to continue taking their drugs. Three separate sources of evidence--postmarket surveillance studies, medical/prescription database studies, and discontinuation of study medication in long-term endpoint clinical trials--support the proposition that angiotensin II antagonists, the newest class of antihypertensives, are well tolerated, and that patients whose initial treatment is an angiotensin II antagonist are more likely to persist with therapy than patients who use other classes of antihypertensives. Recent landmark trials with losartan in hypertensive patients with left ventricular hypertrophy (Losartan Intervention For Endpoint reduction [LIFE]) and in diabetes (Reduction of Endpoints in NIDDM with the Angiotensin II Antagonist Losartan [RENAAL]) demonstrated excellent tolerability, a high level of persistence, and clinical benefits exceeding those provided by blood pressure control alone for the prototype angiotensin II antagonist in clinical settings.