The objective of the Polymer Electrolyte Fuel Cells Annex is to contribute to the identification and development of techniques and materials which can reduce the cost and improve the performance and durability of polymer electrolyte fuel cells (PEFC or, equivalently, PEMFC), direct fuel polymer electrolyte fuel cells (DF-PEFC) and corresponding fuel cell systems. The R&D activities in Annex 31 cover all aspects of PEFC and DF-PEFC, from individual component materials to whole stacks and systems. These activities are divided into three major subtasks: 1) New stack materials Research in the new stack materials aims to develop improved, durable, lower-cost polymer electrolyte membranes, electrode catalysts and structures, catalyst supports, membrane-electrode assemblies, bipolar plates, and other stack materials and designs for PEFC. 2) System, component, and balance-of-plant issues in PEFC systems This subtask includes systems analysis, stack/system hardware designs and prototypes, and modelling and engineering. This subtask also engages in testing, characterization, and standardization of test procedures related to end-user aspects, such as the effects of contaminants on durability, water and heat management, operating environments and duty cycles, and freeze-thaw cycles. The development of fuel processors for PEFC for Combined Heat and Power (CHP) and Auxiliary Power Unit (APU) applications is also addressed in this subtask. 3) DF-PEFC technology. The third subtask focuses on the research and development of DF-PEFC technology, including systems using direct methanol fuel cells, direct ethanol fuel cell, and direct borohydride fuel cells. It involves development of the cell materials, investigation of relationship between cell performance and operating conditions, stack and system design and analysis, and investigation of fuel-specific issues for these direct-fuel polymer electrolyte fuel cell systems.