Distribution of blood pressure (as per US Joint National Committee VI classification and staging criteria) plus awareness, treatment, and control of hypertension were studied in a representative Spanish population sample of 2021 persons (age range, 35 to 64 years). Pressure was determined in accordance with World Health Organization guidelines. A total of 45.1% of subjects were hypertensive (140/90 mm Hg or undergoing drug therapy); 12% had isolated systolic hypertension, and 8.7% had isolated diastolic hypertension. Pulse pressure was 48.7 mm Hg. Heart rate was 81.4 bpm in untreated hypertensives and 78.9 bpm in normotensives (P0.05). A substantial proportion of the community burden of blood pressure was attributable to stage 1 (28.3% of subjects), the most frequent category of hypertension, and to the high-normal blood pressure group (17% of subjects). A percentage breakdown showed that among hypertensives, 44.5% were aware of their condition; of these, 71.9% were undergoing drug therapy, and of those being treated, only 15.5% were controlled (5% of hypertensives). Not only are these figures consistent with the fact that Spain has a higher cerebrovascular mortality than other countries such as the United States, but they represent a great potential for improvement, particularly among those groups registering relatively worse data (younger men, rural residents, and unskilled professionals). A decrease of only 1 to 4 mm Hg in average blood pressure could reduce the prevalence of hypertension in Spain by 12.4% to 15.4%. (Hypertension. 1998;32:998-1002.) Key Words: hypertension, arterial blood pressure prevalence cross-sectional studies awareness A lthough it is well known that arterial hypertension (AHT) is a modifiable risk factor for cardiovascular disease and that there are important differences among developed countries regarding AHT frequency and consequences , countrywide information on awareness, treatment, and control of AHT is still scant. 1-7 Similarly, there is an absence of reporting on new AHT-related cardiovascular risk indicators, such as isolated systolic AHT (ISH), isolated diastolic AHT (IDH), heart rate, and pulse pressure. 2-4 Furthermore, classifications of blood pressure values at progressive levels are used mainly to help in the clinical management of individual patients. 1-4 Yet these same classifications can also serve to highlight the community burden ascribable to the proportions of subjects and blood pressure-related diseases at such levels. 1,5,6 In this regard, US Joint National Committee V and VI (JNC-V and-VI) classifications could prove especially useful because they take into account the fact that blood pressure-related cardiovascular risk is continuous throughout all levels and that risk is thus present at mid-pressure distribution levels, at which the pressures are considered "normal" (high-normal category) or moderately high (stage 1), and in which, because of the high proportion of subjects involved, a sizable percentage of the population's cardiovascular events tend to occur...