An experimental and numerical study of hydrogen effects on the failure of AlZnMg alloys is presented. The material is pre-charged in H and notched samples are loaded at a various strain rates. For the lowest strain rate, brittle intergranular failure is observed. H-effects diminish with increasing strain rate. Beyond a critical strain rate, H-embrittlement is no longer operating and ductile failure is observed. Calculations are carried out to investigate the distribution of H during crack propagation. For low strain rates, the equilibrium distribution of H is always observed. A critical crack propagation rate is evidenced for which the concentration of...