Residual stress has been mapped in the heads of three normal grade and one heat treated (350HT) ex-service railway rails. Transverse, vertical and in-plane shear stresses were deduced using energy dispersive synchrotron X-ray, magnetic permeability and laboratory X-ray measurements. Differences were found between samples both in the distribution of compressive stress introduced at the running surface, and in the locations of the balancing tensile stress below this. The heat treated rail was found to have a thinner layer of surface compression than the normal grade rails, with tensile stress being closer to the active gauge corner. The thinner layer of surface compression in the heat treated rail may reduce the protective benefits for rail integrity that surface compression is thought to confer.