This paper provides an overview of several operating conditions which can have a significant effect on the durability of polymer electrolyte fuel cells (PEFCs) and direct methanol fuel cells (DNTC), including: low reactant flows, high and low humidification levels, and high and low temperatures. The possible effects of these conditions, along with possible mitigating strategies, are discussed. Data from various tests are presented demonstrating lifetimes from 1000 h to greater than 13,000 h for various conditions and applications. (C) 2003 Elsevier B.V. All rights reserved.