The aim of this study was to characterize the prevalence and detection of systemic hypertension in a low income urban area of Mexico City. The population of the studied area was 15,532 inhabitants, of whom 3505 (22.6%) were eligible for study (men aged 35-64 years and non-pregnant women). Home interviews were obtained on 2810 (80.2%) and physical and laboratory examination was performed on 2282 individuals (941 men, 1341 women, 81.2% of those interviewed and 65.1% of all the eligibles). Blood pressure (BP) was measured using a random zero sphygmomanometer (Hawksley, London). Three measurements were made on the right arm after a 5 min rest, with the patient seated. The average of the last two determinations was taken as the patient's BP. High blood pressure (HBP) was defined as systolic BP > or = 160 and/or diastolic BP > or = 95 mmHg, or if the patient was taking antihypertensive therapy regardless of the blood pressure value. A total of 216 subjects (77 men, 139 women) met criteria for HBP. In the 35-44 age group, prevalence for men was 4.16% and for women 3.06%. In the 44-55 age groups the prevalence for men was 7.81% and for women 12.55%. In the 55-64 year group the prevalence for men was 16.51% and for women 22.2%. Obesity was associated with HBP (body mass index in men with HBP was 28.9 kg/m2 vs. without 26.9 kg/m2, p < 0.001; women with HBP, 30.8 kg/m2 vs. without 28.5 kg/m2, p < 0.001.(ABSTRACT TRUNCATED AT 250 WORDS)