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We use splitting in core-refracted teleseismic shear waves (SKS, PKS and similar) to investigate anisotropic properties of the upper mantle beneath the Superior craton in eastern North America and the Yilgarn craton in western Australia. At four sites in each craton we assemble extensive data sets that emphasize directional coverage, and use three different measurement methods to develop mutually consistent constraints on the nature of splitting, and on the likely anisotropic properties that cause it. In both cratons we see evidence of clear directional variation of both delays and fast polarization directions, as well as lateral differences between sites. Relatively small (0.3-0.8 s) amounts of splitting imply weak anisotropy within 150-220 km thick mantle lithosphere. Anisotropy in the asthenosphere likely contributes to splitting in North America where fast directions align with absolute plate motion, but not in Western Australia where fast polarizations and plate motion are nearly orthogonal.