Effects of hydrogen on tensile and torsional strength properties of torsional prestrained ferritic-pearlitic low-carbon steel (JIS-S25C) were investigated. In hydrogen-precharged specimens, hydrogen content increased with torsional prestrain, and was much higher than that in the case of applying tensile prestrain. Tensile strength, reduction of area and torsion angle decreased with torsional prestrain and hydrogen content. In both the tensile and torsion tests, a higher rate of crack initiation and growth was observed in hydrogen-precharged specimens compared to uncharged specimens, and was mainly correlated with the direction of shear stress fracture. The results showed that hydrogen enhances the initiation and growth...