'Hair Growth' is a complex concept which embraces many dimensions: duration of the hair growth-cycle, longitudinal and diameter growth, hair density and pigment content. A diminution in any one of these factors will produce visual thinning and reduce heat insulation. The need to measure hair growth, and the factors which influence it, has been the subject of study in many disciplines, all of which have different needs and therefore require different techniques. The cosmetic scientist has varied and complex measurements compared with the mink farmer who only needs to know when telogen is firmly established before he harvests his pelts to avoid 'shawl alopecia'. A significant contribution to the knowledge of hair biology has been made on animals, partly due to the dictates of finance but also because many animals have orderly and predictable waves of hair growth, unlike the human mosaic pattern. This review will consider the various techniques of growth measurement: duration of the growth-cycle, kinetic studies of the hair root, length and diameter measurements including autoradiography, compound measurements—the Trichogram, and 'pluckability' as this technique has been suggested as an easy cheap measurement of malnutrition which can be performed in the 'field'.