The prevalence of high blood pressure and its treatment was determined in 50 to 59-year-old people in an Australian provincial city (Albury) and in 40 to 59-year-old people in an inner suburb (Brunswick) of Melbourne-Over 90 per cent of those in albury were Australian-born compared with 53 per cent in Brunswick where 25 per cent wre Italian-born. The proportions of people aged 50 to 59 with diastolic blood pressures equal to or greater than 110 mm. Hg together with those on hypotensive therapy were 21.1 per cent in Albury, 22.2 per cent in Brunswick Australian-born and 6.3 per cent in the Brunswick Italian-born. The proportions of those aged 50 to 59 who were on hypotensive therapy were: in Albury 12.0 per cent, among the Brunswick Australian-born 16.3 per cent and among the Brunswick Italian-born 6.3 per cent. About 50 per cent of both the Albury sample and the Brunswick Australian-born people with diastolic blood pressures of 110 mm. Hg or more had never been told that they had high blood pressure. A single postal notification to hypertensive subjects that they should have a further check resulted in 90 per cent attending their general practitioner in Albury within three months but only 60 per cent in Brunswick. The implications of the lower response rates in an inner city suburb are discussed.