The geometries of flow fields have a strong impact on gas distribution in fuel cells. In the present work, a series of customized spiral flow fields were applied to high-temperature polymer electrolyte fuel cells. Pressure tests revealed that a flow crossover occurred in the spiral flow field under consideration, which was caused by the pressure difference between two adjacent channels. Electrochemical characterization indicated that the modified gas distribution compensated the O-2 depletion along the channel and improved the supplement of O-2 in the electrode, as well as the proton conductivity of the electrolyte. The best performances were obtained with a spiral flow field using a channel depth of 1.0 mm. This cell was operated for up to 1000 h under a constant load. The spiral cell exhibited a higher voltage and five times lower degradation rate than a serpentine cell which was analyzed for comparison. This effect was mainly attributed to the modified gas distribution, including the water vapor, which was verified by the computational fluid dynamics analysis. (C) 2013 The Electrochemical Society. All rights reserved.