BACKGROUND: Hypertension is a modifiable risk factor for cardiovascular disease. It affects one in three adults in the United States and contributes to one out of every seven deaths and nearly half of all cardiovascular disease-related deaths in the United States. METHODS: CDC analyzed data from the National Health and Nutrition Examination Survey (NHANES) on the prevalence, treatment, and control of hypertension among U.S. adults aged ≥18 years. Hypertension was defined as an average blood pressure ≥140/90 mmHg or the current use of blood pressure-lowering medication. Control of hypertension was reported as an average treated systolic/diastolic blood pressure <140/90 mmHg. Multivariate analysis was performed to assess changes in prevalence of hypertension, use of pharmacologic treatment, and control of blood pressure between the 1999-2002 and 2005-2008 survey cycles. RESULTS: During 2005-2008, approximately 68 million (31%) U.S. adults aged ≥18 years had hypertension, and this prevalence has shown no improvement in the past decade. Of these adults, 48 million (70%) were receiving pharmacologic treatment and 31 million (46%) had their condition controlled. Although 86% of adults with uncontrolled blood pressure had medical insurance, the prevalence of blood pressure control among adults with hypertension was especially low among participants who did not have a usual source of medical care (12%), received medical care less than twice in the previous year (21%), or did not have health insurance (29%). Control prevalence also was low among young adults (31%) and Mexican Americans (37%). Although the prevalence of hypertension did not change from 1999-2002 to 2005-2008, significant increases were observed in the prevalence of treatment and control. CONCLUSIONS: Hypertension affects millions of persons in the United States, and less than half of those with hypertension have their condition controlled. Prevalence of treatment and control are even lower among persons who do not have a usual source of medical care, those who are not receiving regular medical care, and those who do not have health insurance. IMPLICATIONS FOR PUBLIC HEALTH PRACTICE: To improve blood pressure control in the United States, a comprehensive approach is needed that involves policy and system changes to improve health-care access, quality of preventive care, and patient adherence to treatment. Nearly 90% of persons with uncontrolled hypertension have health insurance, indicating a need for health-care system improvements. Health-care system improvements, including use of electronic health records with registry and clinical decision support functions, could facilitate better treatment and follow-up management, and improve patient-physician interaction. Allied health professionals (e.g., nurses, dietitians, health educators and pharmacists) could help increase patient adherence to medications. Patient adoption of healthy behaviors could improve their blood pressure control. Reducing dietary intake of salt would greatly support prevention and control of hypertension; a 32% decrease in average daily consumption, from 3,400 mg to 2,300 mg, could reduce hypertension by as many as 11 million cases. Further reductions in sodium intake to 1,500 mg/day could reduce hypertension by 16.4 million cases.