Fatigue crack growth behavior from a semi-elliptical surface crack under shear loading has been investigated. The fatigue tests of rectangular bar specimens with a semi-elliptical surface crack were made on an aluminum alloy 2017-T4 and on a weldable structural steel SM41A, using the four-point-shear loading method. Under this loading condition, the crack front of these semi-elliptical surface cracks is subjected to mixed mode II-III deformation, and the ratio of KIII/KII varies depending on the position along the crack front. Macroscopically, two kinds of crack growth morphology-tensile mode growth and shear mode growth-were observed. SM41A showed the tensile mode growth which grew in a plane different from the pre-crack and formed complicated three-dimensional planes. On the other hand, in 2017-T4, the shear mode growth occurred in the same plane as the pre-crack. The planes formed by the tensile mode growth and those by the shear mode growth obtained by the tests have shown good agreement with those predicted by the σmax-criterion and the τmax-criterion, respectively. A method was proposed to predict the shear mode fatigue crack growth in 2017-T4 under mixed mode II-III loading. It was found that, by this method, the da/dN-ΔKτmax relation of a a semi-elliptical surface crack under shear loading can be predicted from the mode II and the mode III fatigue crack growth characteristics, where ΔKτmax=Δ(√(KII2+KIII2).