This retrospective database analysis compared the effectiveness of dihydropyridine calcium channel blockers (DHPs), angiotensin-converting enzyme (ACE) inhibitors, and angiotensin receptor blockers (ARBs) added to diuretics or beta-blockers. Adults with hypertension treated with diuretic or beta-blocker monotherapy between 1998 and 2001 were identifi ed from a large US electronic medical records database of primary care practices. Patients were required to have a baseline blood pressure (BP)>= 140/ 90 mmHg (>= 130/ 80 mmHg for diabetes mellitus) and recorded BP measurements within 6 months before and 1-12 months following index date. Patients were matched 1: 1: 1 by propensity score to correct for differences in baseline characteristics. 1875 patients met study criteria and 660 (220 in each cohort) were matched based on propensity scores. Matched cohorts had no signifi cant differences in baseline characteristics. Mean changes in systolic/diastolic BP were -17.5/-8.8, -15.7/-6.3, and -13.0/-8.0 mmHg with DHPs, ACE inhibitors, and ARBs, respectively. Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High BP 6/7 goal attainment for each regimen was 47.3%, 40.0%, and 32.2%, respectively. DHPs, ACE inhibitors, and ARBs improved BP when added to patients' beta-blocker or diuretic therapy. The greatest benefi ts were observed with DHPs, followed by ACE inhibitors, then ARBs.