This study assesses trends in hypertension prevalence, blood pressure distributions and mean levels, and hypertension awareness, treatment, and control among US adults, age >or=18 years, between the third National Health and Nutrition Examination Survey (1988-1994) and the 1999-2004 National Health and Nutrition Examination Survey, a period of approximately 10 years. The age-standardized prevalence rate increased from 24.4% to 28.9% (P<0.001), with the largest increases among non-Hispanic women. Depending on gender and race/ethnicity, from one fifth to four fifths of the increase could be accounted for by increasing body mass index. Among hypertensive persons, there were modest increases in awareness (P=0.04), from 68.5% to 71.8%. The rate for men increased from 61.6% to 69.3% (P=0.001), whereas the rate for women did not change significantly. Rates remained higher for women than for men, although the difference narrowed considerably. Improvements in treatment and control rates were larger: 53.1% to 61.4% and 26.1% to 35.1%, respectively (both P<0.001). The greatest increases occurred among non-Hispanic white men and non-Hispanic black persons, especially men. Mexican American persons showed improvement in treatment and control rates, but these rates remained the lowest among race/ethnic subgroups (47.4% and 24.3%, respectively). Among all of the race/ethnic groups, women continued to have somewhat better awareness, treatment, and control, except for control rates among non-Hispanic white persons, which became higher in men. Differences between non-Hispanic black and white persons in awareness, treatment, and control were small. These divergent trends may translate into disparate trends in cardiovascular disease morbidity and mortality.