OBJECTIVE To study secular trends in the prevalence and treatment of hypertension in the general population, and the disease course. METHODS Health examinations of cohorts of 50-year-old men in 1963, 1973, 1983 and 1993. METHODS The city of Göteborg, Sweden (about 400,000 inhabitants). METHODS Random population samples of 50-year-old men. METHODS Mean blood pressure (BP) levels in the populations and among treated hypertensives, proportions of hypertensives, and frequency of high BP values (> or = 160/and or 95, and > or = 175/115 mmHg, respectively). RESULTS The mean population BP decreased from 138.4/89.0 mm to 128.7/84.4 mmHg during the 30-year period (p < 0.0001). Mean BP levels among treated hypertensives decreased from 170/113 to 142/94 mmHg (p < 0.0001), and the proportion of men with high BP values diminished from 3.9 to 0.1%. Also BP levels among normotensives decreased significantly (p < 0.0001). CONCLUSIONS The findings could partly be seen as a result of successful case-finding and treatment of hypertension in the region, but alteration of the natural course of hypertension cannot be excluded.