High speed, high resolution infrared thermography, as a non contact, full field, and nondestructive technique, was used to study the temperature variations of a cobalt based ULTIMET alloy subjected to cyclic fatigue. During each fatigue cycle, the temperature oscillations, which were due to the thermal elastic plastic effects, were observed and related to stress-strain analyses. The change of temperature during fatigue was utilized to reveal the accumulation of fatigue damage. A constitutive model was developed for predicting the thermal and mechanical responses of ULTIMET alloy subjected to cyclic deformation. The model was constructed in light of internal state variables, which were developed to characterize the inelastic strain of the material during cyclic loading. The predicted stress-strain and temperature responses were found to be in good agreement with the experimental results. High speed, high resolution infrared thermography, as a non contact, full field, and nondestructive technique, was used to study the temperature variations of a cobalt based ULTIMET alloy subjected to cyclic fatigue. During each fatigue cycle, the temperature oscillations, which were due to the thermal elastic plastic effects, were observed and related to stress-strain analyzes. The change of temperature during fatigue was utilized to reveal the accumulation of fatigue damage. A constitutive model was developed for predicting the thermal and mechanical responses of ULTIMET alloy subjected to cyclic deformation. The model was constructed in light of internal state variables, which were developed to characterize the inelastic strain of the material during cyclic loading. The predicted stress-strain and temperature responses were found to be in good agreement with the experimental results.