As the initial step of a large randomized trial to test a new strategy of caring for hypertensive patients, the state of blood pressure screening was studied in 34 community-based family practices in southwestern Ontario. The charts of all active adult patients, 20-65 years of age, were reviewed.At least one blood pressure reading was recorded in the last five years for 71% of the 40,453 patients. The proportion of patients screened increased with age; in each age group, a greater proportion of females than males had been screened. Overall, 8.9% of males and 9.6% of females were labelled hypertensive. The rate of patients so labelled increased with age to a maximum of 30% of the 55-65 age group. More than 50% of patients with diastolic pressures over 105 mm Hg were not taking hypotensive drugs.