Stress corrosion cracking of certain 7079-T6 aluminum alloy aircraft structures involving sustained tensile stress acting in an unfavorable grain direction has occurred sometimes in surprisingly mild environments. The resistance of short-transverse specimens of 7079-T6 products has been evaluated at different levels of applied stress in several different seacoast and inland industrial atmospheres. It was found that the atmosphere was more critical than the generally accepted alternate-immersion test using 3.5 per cent sodium chloride. The results of the outdoor tests are correlated with eight accelerated exposures; and consideration is given to the most suitable laboratory stress corrosion test environment for this alloy. A detailed analysis of the constant deformation methods of stressing is included.