This study focuses on the microscale fatigue properties of 316L stainless steel. This material is commonly used in the manufacture of medical devices such as stents, which, once implanted, are subjected to hundreds of millions of fatigue cycles. Fatigue testing was carried out on 50 gm, 75 mu m,100 gm and 150 gm 316L specimens with 60 gm thickness. A size effect was shown to exist in the form of a reduced fatigue endurance limit of the 50 gm specimens. In order to determine the cause of this size effect, the outer surfaces and fracture surfaces of failed test specimens were examined using Scanning Electron Microscopy (SEM) techniques. These SEM studies suggest that the process of strain localization was occurring in the specimens and was most pronounced in the 50 gm specimens. The experimentally established surface roughness of the test specimens, measured using white-light interferometry, further confirmed the SEM observation. (C) 2016 Elsevier Ltd. All rights reserved.