The corrosion behaviors of austenitic stainless steels in high-temperature boric acid solutions were studied to estimate the effect of boric acid on the general corrosion rate in high-temperature water and on the stress-corrosion cracking in high-temperature chloride solution. The general corrosion rate in static or dynamic water was not so much affected by the existence of boric acid, and the average corrosion rate for 10, 000 hours was about 2mg/dm2. month at 300°C. The stress-corrosion cracking in sodium chloride solution was diminished by the existence of boric acid. The general corrosion rate and the stress-corrosion cracking were suppressed by the addition of a small amount of potassium hydroxide.