Weld joint of a low alloy CrMoV cast steel used in steam turbine casings has been characterized by the dynamic fracture toughness parameter, KId, through testing of precracked Charpy V-notch impact specimens on an instrumented impact test equipment. Influence of the relative orientation of fatigue precrack front and the weld zones on KId is investigated in addition to individual zone analysis. A composite weld joint with crack front enveloping all the three zones simultaneously is found to be an appropriate configuration for conservative fracture mechanics based design analysis. Crack tolerance capacities for each of the weld configurations investigated are illustrated. © 1988.