Influence of loading history on the mechanical properties for polyethylene (PE) was examined through an experimental study, in which each specimen was subjected to two short-term tensile tests that were conducted at least 1 month apart. The first test was to apply various loading histories to specimens, and the second test to characterize the corresponding change in mechanical properties. The results show clearly that the loading history introduced in the first test affects mechanical properties measured from the second test. In particular, the initial tangent modulus and stress response to deformation from the second test show a noticeable decrease with the increase of the applied strain introduced in the first test, even at the applied strain for the first test as low as 0.05. Change in mechanical properties was also found to depend on loading mode (cyclic and monotonic) and crosshead speed (1 mm/min and 5 mu m/min) used in the first test. The above changes are explained based on the microstructural concept of interphase that is located in the interlamellar region and has a less ordered microstructure than the crystalline lamella. Based on results from this study, further investigation is planned to obtain direct evidence to support the idea. POLYM. ENG. SCI., 55:2002-2010, 2015. (c) 2014 Society of Plastics Engineers