In steel Weld.s, the development of residual stress is often complicated by the solid state phase transformations that occur upon cooling. Here the authors present bulk residual stress distributions, as measured by neutron diffraction, for the configuration of a single pass gas tungsten arc Weld. bead deposited on to a 20 mm thick SA508 steel substrate. Two specimens were manufactured, one with a low heat input (1-2 kJ mm-1) and another with a high heat input (2-4 kJ mm-1). The resulting microstructures and residual stress distributions are discussed in terms of the differing thermal excursions across each Weld. In regions that are austenitised during Welding, the transformation strain on cooling is shown to compensate in part for thermal contraction strains. Accordingly, phase transformations in SA508 steel led to significant reductions in stress within the Weld. bead and much of the heat affected zone, while the highest tensile stresses were located immediately outside the heat affected zone boundary in the untransformed region. © 2000 Institute of Materials, Minerals and Mining.