Fuel cells are currently being explored as energy conversion devices which can meet a range of societal needs for transportation, stationary and portable power. Among the various types of fuel cells under consideration, polymer electrolyte membrane fuel cells (PEMFCs) are a leading technology. The dominant class of polymer electrolyte membranes currently in use are perfluorinated, poly(tetrafluoroethylene)-based polymers bearing perfluoroether side chains which terminate in a sulfonic acid group, or perfluorosulfonic acids (PFSAs). A critical issue for commercial success of PEMFCs is their durability. From the literature it is unclear whether there is a single, dominant mode of failure for PEMFC systems. The majority of authors in the field attribute chemical degradation of PFSA membranes to be caused, at least in part, by exposure to peroxide and hydroperoxide radicals known to be produced in these electrochemical devices. The present study attempts to develop a coherent model of PEM polymer degradation mechanisms. In order to gain the benefit of standard chemical methods generally not easily deployed when studying the intractable ionomers, a family of low molecular weight model compounds with structural characteristics similar to moieties found in PFSAs was examined. In parallel we studied degradation of a leading PFSA membrane. Relative kinetics of fluoride generation, as well as characterization of degradation products were considered as mechanistic probes.