The fatigue behavior of Ag films on polyethyleneterephthalate substrates was studied using electrical resistance measurements. Scanning electron microscopy images showed two types of failure: typical fatigue failure with extrusion-intrusion pairs, and ductile failure with local necking. Once through-thickness cracks are formed in the metal layer, cracks propagate and the resistance increases abruptly for both failure modes. The effect of adhesion on fatigue life is discussed in terms of concurrent delamination, crack initiation and propagation. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.