Mercury sphygmomanometry, the most widely used indirect method of blood pressure measurement, derived from the work of Scipione Riva-Rocci and Nicolai Korotkov forms the basis of our knowledge of the epidemiology of high blood pressure. Thus, recognised hypertension was first described as a specific clinical entity associated with an increased risk of strokes in the middle aged and elderly. However, it is now known that hypertension is a quantitative and not a qualitative deviation from the norm, and that there is no natural dividing line between normal and abnormal pressures.