The aim of this study was to assess the prevalence, awareness, treatment and control of hypertension among subjects above the age of 39 years living in the urban area of Oporto, Portugal. One hundred and seventy seven individuals from the community were selected by random digit dialing. Each subject was asked about his/her personal history of hypertension, antihypertensive treatment and had his/her blood pressure measured. The prevalence of hypertension was 57.1%, defined by systolic blood pressure (SBP) > or = 140 mm Hg and/or diastolic blood pressure (DBP) > or = 90 mm Hg and/or administration of current the antihypertensive medication. If the values defining hypertension were SBP > or = 160 mm Hg, and DBP > or = 95 mm Hg the prevalence would be 37.9%. The overall prevalence of hypertension was higher in females, but a slightly higher non significant value was found in males in the fifth and sixth decades. Among hypertensives, 62.7% were aware of their condition, 56.7% were treated, 84.2% of hypertensives treated were controlled (SBP < 160 mm Hg and DBP < 95 mm Hg) and 44.7% were very well controlled (SBP < 140 mm Hg and DBP < 90 mm Hg). The question "Are you hypertensive?" had a sensitivity of 62.7%, a specificity of 83.6% and an accuracy of 75.7%. In the preliminary results of this study of an urban population with a high prevalence of hypertension, the awareness of hypertension is similar to that described in the United States of America twenty years ago, the percentage of hypertensives treated is similar to the American percentage fifteen years ago and the percentage of hypertensives treated and controlled is close to the current American percentage.