The effectiveness of a quality improvement program for hypertension management practices and patient health outcomes in a group-model managed care organization was evaluated. Health-system pharmacists analyzed medical and pharmacy claims data to identify hypertensive patients. Chart review was conducted on a random sample of these patients to validate a hypertension diagnosis and to obtain blood pressure (BP) control rates and prevalence of cardiovascular risk factors and comorbid conditions. The interventions consisted of educating health care providers and recommending appropriate pharmacotherapy for compelling indications. Patient outcomes were compared with baseline hypertension data. After interventions were implemented, medical and pharmacy claims identified 30,721 hypertensive patients and chart reviews were performed on a random sample of 417 patients. Pharmacy claims revealed a total of 193,311 anti hypertensive prescriptions. Approximately 47% of all hypertensive patients were managed with mono-therapy, while 24% received dual therapy, and 11% were taking three or more antihypertensive medications per day. Of the patients on monotherapy, 93% received an angiotensin-converting-enzyme inhibitor (27.3%), diuretic (26.6%), beta-blocker (23.4%), or calcium channel blocker (15.4%). The overall level of BP control significantly improved from 37.2% at baseline to 49.2% at follow-up (p = 0.0007). BP control in the follow-up evaluation was 22.2% in diabetic, patients. For treatment of patients with co-morbid disease states, provider practice patterns were evaluated at baseline and follow-up. Improving the quality of hypertension management increased BP control from 37.2% to 49.2%. Continued efforts to improve hypertension management, particularly in patients with concomitant diabetes and in elderly patients with isolated systolic hypertension, are needed.