We studied whether changes in recognition and control of hypertension could be detected in the population of Rochester, Minn, from 1950 to 1979, a period in which a major decrease in the incidence rate of stroke was observed. Prevalence of diastolic blood pressure greater than or equal to 105 mm Hg fell 26% and 70% in men and women, respectively, between 1950 to 1959 and 1970 to 1979. Prevalence of pressures greater than or equal to 95 mm Hg decreased 5% in men and 58% in women. Increasing control of hypertension had an almost inverse linear relationship with the decreasing incidence of stroke in women, but the incidence of stroke in men did not decrease until ten years after improvement in the control of blood pressure began. We conclude that improvements in the detection and control of hypertension contributed to the declining incidence of stroke and that differences in management of hypertension could account for the difference between men and women in the trend of stroke decline.