Thermo-mechanical fatigue (TMF) in AISI 304L stainless steel is investigated in two temperature ranges using four phase differences between the mechanical loading and the temperature. In the temperature range from 450 degrees C to 700 degrees C. the fatigue life was lowest in the in-phase condition. However, in the temperature range from 400 degrees C to 650 degrees C, the minimum fatigue life occurs in the counter-clockwise-diamond condition. Estimation of creep strains occurring in the TMF cycle based on the monotonic creep tests predicts the highest creep strains in the in-phase conditions in the two temperature ranges, but cannot explain the minimum life in the counter-clockwise-diamond condition in the lower temperature range. This phenomenon is explained qualitatively by the operation ranges of dynamic strain aging and the creep of this material and their competition in the TMF cycle. This explanation predicts the highest influence of the creep in the counter-clockwise-diamond condition in the temperature range of 400-650 degrees C. (C) 2011 Elsevier B.V. All rights reserved.