We made an inventory of 19 studies that have been or are being undertaken to better characterize the distribution of ambulatory blood pressure in the population at large or in larger groups of individuals selected from the population. No study was without some degree of selection in the recruitment of its subjects, but none of the subjects was selected or excluded on the basis of ambulatory blood pressure. These studies could provide the data required to define more precise, age- and sex-specific, diagnostic criteria for ambulatory blood pressure measurement in day-to-day clinical practice.