Hypertension and diabetes mellitus are common diseases in the United States. Patients with diabetes have a much higher rate of hypertension than would be expected in the general population. Regardless of the antihypertensive agent used, a reduction in blood pressure helps to prevent diabetic complications. Barring contraindications, angiotensin-converting enzyme inhibitors are considered first-line therapy in patients with diabetes and hypertension because of their well-established renal protective effects. Calcium channel blockers, low-dose diuretics, beta blockers, and alpha blockers have also been studied in this group. Most diabetic patients with hypertension require combination therapy to achieve optimal blood pressure goals. (Am Fam Physician 2002;66:1209–14. Copyright © 2002 American Academy of Family Physicians.)