ObjectiveTo assess the trends in blood pressure (BP) and in body mass index (BMI) in the hypertensive and normotensive population in Finland during 1982–1997.DesignFour independent cross-sectional standardized population surveys were conducted in 1982, 1987, 1992 and 1997.SettingThe provinces of North Karelia and Kuopio in eastern Finland and the region of Turku-Loimaa in southwestern Finland.ParticipantsMen and women aged 25–64 years were selected randomly from the national population register. The participants were classified into four groups according to their BP level and treatment status: normotensive, unaware hypertensive, aware but untreated hypertensive and treated hypertensive. The total number of participants was 24 083.Main outcome measuresThe means of systolic BP (SBP), diastolic BP (DBP) and BMI, as well as the distribution of BMI among the four study groups were measured.ResultsMean SBP decreased significantly in all groups. The fall in DBP was significant only in drug-treated hypertensive men and women (P<0.001). Mean BMI increased significantly in all groups except in aware hypertensive women receiving no antihypertensive drug treatment. The proportion of obese subjects (BMI >30 kg/ m2) increased most in aware hypertensive men and in drug-treated hypertensive women.ConclusionsThe prevalence of obesity has increased significantly in normotensive and particularly in hypertensive Finns during the past 15 years. There is an urgent need for more effective measures for weight reduction in obese hypertensive patients in primary healthcare, and for the prevention and control of obesity in the whole population.