Hypertension and its consequences continue to threaten the health of as many as 60 million Americans. Effective control of blood pressure can be achieved in some patients with a single agent and in many of the remainder with combination therapy. The ideal combination regimen is one that is at least as effective as a single agent, has minimal or no side effects, has a wide therapeutic index, is simple to administer, and is effective in a wide variety of patient populations. When used in combination, the thiazide diuretics and the angiotensin-converting enzyme inhibitors have been shown to improve blood pressure reduction over either drug used alone. In addition, the combination is effective in a wide range of patient populations (blacks and whites, young and old) and is accompanied by fewer adverse metabolic effects than the thiazides alone. Finally, the combination has a more positive impact on quality of life than other combinations involving the thiazide diuretics.