Martensitic advanced high strength steel(MS-AHSS)belongs to a new class of steels that are currently used in the manufacture of lightweight yet crashworthy cars.One issue with using high-strength steels is hydrogen embrittlement(HE),which causes the degradation of the mechanical propertiess of the steel.This study investigated the influence of hydrogen on the mechanical and fracture properties of four commercially-produced martensitic advanced high strength steels(MS-AHSSs),using linearly increasing stress tests(LISTs).The four steels had tensile strengths above 950 MPa.Electrochemical hydrogen charging was carried out in 0.1 M NaOH at cathodic potentials of ?1200,?1500 and ?1800 mVAg/AgCl.The LIST sused two appliedstress rates.The four MS-AHSSs had microstructures consisting of martensite and ferrite.Hydrogen had little effect on the threshold and tensile stress but decreased ductility.HE susceptibility increased with increasing steel strength,more negativecharging potential,and decreasing applied stress rate.Two grades of MS-AHSS showed little HE susceptibility,whilst the two strongest ones exhibited some susceptibility.HE susceptibility was manifest by the reduction of ductility,and the change from ductile cup-and-cone fracture to macroscopically-brittle shear fracture.The LISTs were proven capable of assessing HE susceptibility in MS-AHSS.