If the rate of appearance of publications in the field can be taken as a criterion, hemorheology can be considered as coming of age in the fairly recent past - perhaps forty or so years ago. This relative lateness is due largely to the previous lack of measuring equipment with the required sophistication; a particular problem being the complex nature of blood viscosity and the need for adequate viscometers capable of measuring it. Nevertheless the ease of availability of blood, its dramatic color and its obvious connection to well being have made it a subject of study since ancient times. What is more, many of those ancient studies were of physical properties of blood that have direct hemorheological relevance. So it could be said that hemorheology is one of the oldest of clinical research areas.