Blood pressure (BP) is controlled to recommended levels in only 1 in 3 people with hypertension, and there has been little improvement since the late 1980s, despite advances in evidence to support aggressive hypertension control, and availability of many new and effective antihypertensive drugs. It is clear that meaningful and sustained improvement in hypertension control will likely require fundamental changes in the current physician-centered office-visit based model of caring for hypertension. In this project we develop and implement an intervention that takes advantage of new technology and team models of care to improve BP measurement and control, solving the problems that have limited the application of case management approaches to hypertension care improvement. The study will take place in a diverse population of adults with hypertension cared for in a real-world primary care setting. The Telemonitoring Intervention (TI) integrates 2 innovative components: First, home BP measures are done using state-of-the-art modem-enabled automated equipment that internally stores and electronically transmits BP data through a simple touch-tone telephone connection to a secure web site. Second, a pharmacist case manager integrated with the primary care team through a jointly used electronic medical record (EMR) and formulary adjusts antihypertensive therapy using an approved written protocol, under a collaborative practice agreement with physicians. Treatment decisions are based on home BP data and are discussed and communicated to patients in telephone visits with the pharmacist case manager. Two-way communication between the pharmacist case manager and the patient's primary care team is assured by using a shared EMR and by additional secure messaging of the results of every pharmacist encounter to the primary care team. To assess the impact of the TI on hypertension control, patient satisfaction, and costs of care, we will conduct a cluster-randomized trial, assigning 16 primary care clinics and 450 of their nested patients with uncontrolled hypertension to either a Usual Care (UC) control group or TI. Blood pressure outcomes in both groups will be determined at baseline, 6, 12, 18 and 54 months in an identical and blinded fashion in a research clinic separate from the clinical setting where patients received their medical care. We hypothesize that guideline BP control will be achieved at 6 months and maintained at 12 months in more than 60% of patients from TI clinics, compared to < 40% in patients from UC clinics. We will compare satisfaction with care and costs in the TI and UC groups. The TI has the potential to improve hypertension control for millions of patients, and could be implemented widely in diverse and large patient populations based on performance in this randomized trial. The results of the project will have important implications for future efforts to improve care provided to many of the estimated 20 million Americans with uncontrolled hypertension.