Hydrogen absorbed from the test environment was successfully detected from Al-Zn-Mg-Cu and Al-Mg-Si base alloys deformed in laboratory air, which is a direct evidence of hydrogen induced degradation. The experimental results support the idea that hydrogen absorbed from the environment caused initiation of intergranular crack at specimen surface and subsequent premature failure, however, details in fracture process were different between Al-Zn-Mg-Cu and Al-Mg-Si alloys. The possible mechanism by which hydrogen affects the fracture process was discussed.