Abstract: Hydrogen-induced cracking could initiate but Only propogate a small amount in a precharged WOL specimen of Ti-24Al-11Nb alloy at room temperature. The K_IH and da/dt of hydrogen-induced cracking in hydrogen gas at 400℃, however, could be measured. Hydrogen-induced cracking on the surface initiated discontinuously within the plastic zone when the plastic deformation developed to a particular and reproducible extent, which was similar to that of the Cleavage crack in an uncharged specimen with increasing K_I. The fracture surface of hydrogen-induced cracking in hydrogen gas at 400℃ was in close relationship with microstructure and basely identical with that of overload failure at room temperature but was more brittle than that of overload failure at 400℃ for all microstructures