AbstractInternal or residual stresses have been defined by Orowan1(a) as those existing in bodies upon which no external forces are acting. They can arise out of unequal plastic deformation, causing a misfit of the elements on removal of the load; alternatively, a chemical change may alter a part of the body and similarly produce residual stresses. There are, of course, many other ways of obtaining these stresses, but this review is concerned with their measurement and it is not intended to elaborate further.