The investigations were concerned with the effects of water vapor and temperature on the long-term mechanical strengths of alumina ceramics. Mechanical tests were therefore made over a large temperature range (-196 to 1100C) in dry, humid, and saturated atmospheres. A fatigue theory involving stress corrosion of an elastic continuum has been applied to the low-temperature experimental data on sapphire. Reasonible values for the parameters involved in the theory were obtained.