One plausible reason for the decline in cardiovascular disease (CVD), and in particular stroke, in the last century is population reductions in blood pressure. Blood pressure tracks from childhood into adulthood, and early-life blood pressure is associated with increased cardiovascular risk but few studies have reported on blood pressure trends among young individuals who are free of CVD and not taking antihypertensive medication. Knowledge of such trends may improve understanding of the causes of hypertension and enhance prevention. We report that declines in blood pressure have been taking place in high-income countries in 5 to 34-year-olds of both sexes and from a range of ethnic groups for at least the last 50 years, indicating that exposures acting in early life are important determinants of blood pressure. Possible explanations for these favourable trends include improvements in early-life diet and there is also intriguing evidence suggesting that blood pressure may be programmed by sodium intake in infancy. Occurring throughout the blood pressure distribution, these trends may have made important contributions to declining CVD rates. There may therefore be scope for intervening in early life to prevent high blood pressure in adulthood, and the downward trends reported in several recent studies suggest that the prevalence of adult hypertension and cardiovascular risk will continue to decline. However, persisting high rates of CVD in the developed world, the impending CVD epidemic in developing countries, along with increasing childhood obesity, and the possibility that favourable blood pressure trends may be plateauing point to the need for enhanced measures to control blood pressure, and for further research to improve understanding of its determinants.