Many epidemiological studies have addressed various aspects of blood pressure, ranging from descriptions of normal blood pressure distributions in different populations to the influence of age and other factors on blood pressure. However studies consider blood pressure in terms of hypertension, assessing prevalence, treatment and control of hypertension in diverse populations. Very few studies are available dealing with the distribution of blood pressure values in population as percentiles, none of which is from Europe and none of which addresses a wide age range, sex and coexisting cardiovascular risk factors. Therefore, main aim of this thesis was to examine in detail the distribution of blood pressure of a large cross sectional study sample of 35,869 women and men aged 18-99 years. The second aim was to validate the observed age-effects in the cross-sectional German Metabolic and Cardiovascular Risk Study, in the independent, longitudinal and population-based Heinz Nixdorf Recall study, using baseline and 5 year follow up data of 4,157 men and women, aged 45-75 years. This study showed an age-related increase of the systolic blood pressure in all percentiles in both men and women, independent of the intake of antihypertensive medication, and/or presence of Cardiovascular Disease (CVD) or CVD risk factors. This is the first study to provide detailed information on the population distribution of blood pressure readings relating to both sexes, very old individuals and CVD risk factors. Furthermore, the age related increase observed in the systolic blood pressure in the cross sectional study could be confirmed for men and women, aged 45-75 years in the independent, longitudinal Heinz Nixdorf Recall study.