The fracture toughness of two high-chromium white iron alloys in the as-cast condition has been investigated. Fracture toughness test pieces were extracted at various orientations relative to the columnar macrostructure. The toughness of a 27 Cr white iron alloy was very sensitive to orientation, and the toughness was much larger when the crack propagated in a direction perpendicular to the long dimension of the eutectic carbides. The toughness of the 15-3 Cr-Mo white iron was insensitive to the orientation. The different fracture behaviour of the two alloys was related to the anisotropy of the eutectic carbide structures in the as-cast material. The limitations in applying quantitative data on the eutectic carbide structure to models of fracture toughness in white iron alloys were illustrated.