The Hypertension Detection and Follow-up Program (HDFP), a national collaborative study, screened approximately 159,000 people for high blood pressure in 14 communities between 1973 and 1974. Results show that detection, treatment, and control of high blood pressure has improved considerably since the 1960s. Whereas in the past about half of all hypertensives knew they had high blood pressure, half of those detected were under treatment, and half of those under treatment had their high blood pressure under control, the corresponding percentages in the 14 HDFP communities a decade later indicate that 75% of hypertensives were detected, 72% of those were under treatment, and 70% of those under treatment had a diastolic blood pressure under 95 mm Hg. While the differences in prevalence of hypertension are between races rather than sexes (with black individuals in some age groups being about twice as likely as white individuals to have hypertension), the differences in detection and treatment rate are largely between sexes and not between races. Women are considerable more likely to be aware of their hypertension, to be under treatment for it, and to have their high blood pressure under control. Rates of control vary considerably among age-sex-race subgroups, from only 8% of white male hypertensives aged 30-39 to 67% of white female hypertensives aged 60--69. It appears that although efforts to combat this disease over the past decade have probably made considerable progress in improving the recognition and treatment of high blood pressure, there remain a large number of undetected, untreated, and uncontrolled hypertensives.