A systematic approach involving experiments and dynamic elastic-plastic finite element analyses was used to investigate the problem of crack initiation, propagation, and arrest in weldments under rapidly applied loading. The aim was to develop a predictive capability that can be used to assess the risk of fracture in welded structures subjected to blast loading. The experimental effort included residual stress measurements on welded HY-80 steel specimens together with a series of explosive loading experiments performed after precracking these specimens. Measurements were made of the time of crack growth initiation and the extent of crack growth at arrest. Elastic-thermoplastic finite element computations were made to obtain the weld-induced residual stresses. With these as initial conditions, dynamic elastic-plastic computations were then performed to predict crack initiation and growth behavior under the measured explosive loading history. These computations used estimates of the running fracture toughness based on fracture toughness data for HY-80 weldments available in the literature. Reasonably good agreement was obtained with the observed results. Of possible greater significance for subsequent fracture mechanics analyses of weld defect problems, it was found that the presence of weld-induced residual stresses strongly affects the prediction of the crack length at arrest.