In this work, we investigated experimentally the effect of the anode flow field design on the performance of a DMFC. Single serpentine (SSFF) and parallel flow fields (PFF) with different sizes were designed, fabricated and tested. The experimental results showed that the DMFCs equipped with the SSFFs yielded better performance than those with the PFFs. It was also found that gas bubbles blocked the flow channels in the PFF at low methanol solution flow rates and high current densities, but this channel-blocking phenomenon was never found in the SSFF under all the test conditions in the present work. Studies on the effects of SSFF design parameters revealed that both open ratio and flow channel length had significant influences on the cell performance and pressure drop. An open ratio of around 50% led to the best cell performance at moderate and high methanol solution flow rates. However, at low methanol solution flow rates, a larger open ratio yielded a higher power density at higher current densities, corresponding to the mass transfer limitation region. In addition, it was found that a longer flow channel usually gave better cell performance, but caused a larger pressure drop. © 2004 Elsevier Ltd. All rights reserved.