Internal friction peaks associated with the presence of hydrogen in eight types of high chromium-nickel alloy steel were observed in measurements with a torsion pendulum. The optimum temperature for maximum internal friction lies between 610-640℃ for a frequency of vibration of about 1.5 cycles per second. Systematic investigations were made with specimens containing 18% of Cr and 12% of Ni. The elementary process for this internal friction peak was found to be a relaxation process, associated with an activation energy of about 46,000-50,000 calories per mole. Judging from the value of this activation energy, as well as from the behavior of the internal friction peak when the measurements were taken while the temperature was raised, lowered and kept constant, the conclusion was reached that the new internal friction peak is associated with the stress-induced micro-diffusion of hydrogen molecules in high alloy steels.Internal friction measurements were also able to disclose the temperature range in which transformations between hydrogen molecules and hydrogen atoms are taking place in 18 Cr 12 Ni alloy steel specimens for a given rate of heating and cooling. The results obtained are in agreement with those found in the literature.