Detection of hypertension and blood pressure control are critically important for reducing the risk of heart attacks and strokes. We analyzed the trends in the prevalence, awareness, treatment, and control of hypertension in the United States in the period 1999–2004. We used the National Health and Nutrition Examination Survey 1999–2004 database. Blood pressure information on 14 653 individuals (4749 in 1999–2000, 5032 in 2001–2002, and 4872 in 2003–2004) aged ≥18 years was used. Hypertension was defined as blood pressure ≥140/90 mm Hg or taking antihypertensive medications. The prevalence of hypertension in 2003–2004 was 7.3±0.9%, 32.6±2.0%, and 66.3±1.8% in the 18 to 39, 40 to 59, and ≥60 age groups, respectively. The overall prevalence was 29.3%. When compared with 1999–2000, there were nonsignificant increases in the overall prevalence, awareness, and treatment rates of hypertension. The blood pressure control rate was 29.2±2.3% in 1999–2000 and 36.8±2.3% in 2003–2004. The age-adjusted increase in control rate was 8.1% (95% CI: 2.4 to 13.8%; P =0.006). The control rates increased significantly in both sexes, non-Hispanic blacks, and Mexican Americans. Among the ≥60 age group, the awareness, treatment, and control rates of hypertension had all increased significantly ( P ≤0.01). The improvement in blood pressure control is encouraging, although the prevalence of hypertension has not declined.