AbstractThe technique of neutron strain scanning is describedand its application to through surface measurement of the residual stress field of metal components is discussed.The technique is particularly suitable for non-destructive internal strain and stress mapping since the neutron is a relatively penetrating particle and measurements an be made, in principle, at any point in any orientation throughout a component, subject to neutronbeam attenuation and spatial resolution constraints. The technique is less well suited to measurements made olely in the outermost surface layers but may be used to obtain data through the surface into a component,provided instrumental surface effects are allowed for during data processing or are reduced to negligible values by instrument design and careful measuring procedures. Illustrative examples are given of experimentalresults obtained on a series of metal components, including autofrettaged tubes, new and used railway rails, and peened surfaces in which steep near surface stress gradients are observed.