The results suggest three stages in the stress corrosion process with the rate of penetration of corrosion or cracking increasing with each succeeding stage. In the first stage, stress corrosion takes place independently of stress, that is, it follows the same course as the general corrosion of an unstressed specimen; for the alloys investigated this general corrosion occurred as random pitting. In the second stage, the attack becomes intergranular (if not already of this type) and directional, and it leads to the development of cracks of a microscopic size, or larger; these are the secondary cracks frequently seen in specimens that fail by stress-corrosion cracking. The third stage initiates whenever one of the intergranular cracks developed in the second state progresses far enough for the yield strength of the specimen to be reached; and it continues to the point of tensile failure.