Damage identification due to fatigue has been studied on 304-Stainless Steel and Al-Cu-Mg alloys 2014-T651 and 7175-T7351, using two different experimental methods: a) cyclic indentation, and b) infrared thermography. Indentation response during load controlled cyclic loading is used to characterize fatigue response of materials. The load vs. depth of penetration data obtained continuously during fatigue testing is used to obtain information on cyclic stress-strain behavior and onset of failure. Infrared thermography is used to study the heat generation during fatigue loading on specimens. The variables that affect the process are: frequency of loading, magnitude of strain (elastic-plastic), thermal properties. The temperature curve can be considered to be having three regions, initial region of rapid increase in temperature, followed by stable temperature rise and final rapid heat generation prior to failure. The slopes in the initial region and stable region are independent of prior damage history in materials in case of specimens subjected to pure elastic load reversals. In case of elastic-plastic loadings, the rate at which the temperature rises in initial region changes as a function of fatigue damage and can thus be used to estimate prior damage in materials. © 2010 TIIM, India.