Operating a passive direct methanol fuel cell (DMFC) with concentrated methanol is to achieve its inherently appealing feature of high specific energy. The objective of this work is to understand and identify key system design parameters that influence the performance of the passive DMFC operated with concentrated fuel at different operating temperatures. The design parameters that were investigated include the open ratios of the perforated polytetrafluoroethylene (PTFE) sheet, and the anode gas diffusion layers (GDL) and the cathode filters. Experimental results show that with the neat methanol operation, a medium open ratio is required to achieve high cell performance. It is interesting to find that unlike the passive DMFC operating with diluted fuel, an increase in the operating temperature from 40 to 60 degrees C results in a decrease in the cell performance due to water starvation. In addition, it is demonstrated that the anode GDL has little influence on the cell performance, but the effect of cathode filters is much more significant. Finally, the constant-current discharge test indicates that the supply of methanol becomes a key factor leading to performance degradation during the long-term operation. (C) 2014 Elsevier Ltd. All rights reserved.