General information of the conditions under which 18-8 stainless steels corrode aids in establishing conditions to minimize failure in this and similar steels. Detailed study was made of the effect of temperature, concentration, and pH of aerated sodium chloride solutions, noting the nature of corrosion and corrosion rate for 24-hour periods. Corrosion of 18-8 increases sharply with temperature, going through a maximum at approximately 90°C. for 4 and 10 per cent sodium chloride and above 90°C. for 1 per cent solution. Corrosion is by pitting. At the boiling point corrosion decreases to nearly zero in 24-hour tests owing to lack of dissolved oxygen.Increased salt concentration at 90°C. increases corrosion of 18-8 from zero in distilled water to a maximum at 4 per cent sodium chloride. Identical tests with mild steel show significant corrosion in distilled water and maximum corrosion in 2 per cent sodium chloride. At higher concentrations corrosion is less, dropping off more rapidly for mild steel. In 25 per cent solution the corrosion rates of 18-8 by pitting and mild steel by uniform solution approach each other. At 90°C. in 4 per cent sodium chloride the logarithm of corrosion weight loss is a linear function of pH in the range pH 12 to 8. Corrosion falls off rapidly below pH 5, goes through a minimum at 2.9 to 4.5, and increases sharply at 2.9. Pitting is observed above pH 2.8, and uniform solution accompanied by hydrogen evolution occurs in more acid solutions. The number of pits per square decimeter follow the minimum and Vol. 33, No. 7 maximum of corrosion plotted with pH. Maximum pit penetration occurs at pH 6 to 7.The effects of pH in the alkaline region are explained on the basis of increasing effective cathode areas surrounding the pits with decrease in pH. The corrosion minimum is accounted for by partial breakdown of passivity. The sharp upturn of corrosion at pH 2.9 is due to corrosion by hydrogen evolution.The results indicate that at 90°C. corrosion of 18-8 in aerated sodium chloride solutions is less if the solutions are made acid to pH 3 or 4. Least corrosion occurs in the alkaline region of pH 12.