This paper evaluates proton exchange membrane (PEM) fuel cell microchannel width and depths ranging from 20μm to 1000μm. A DRIE process is employed to create the serpentine microflow field patterns from silicon wafers for channel width and depths ranging from 20μm to 200μm. To compare the smaller microchannel dimensions with conventional dimensions, computer numerical control (CNC) machining was used to create the 500μm and 1000μm flow field channel dimensions in delrin. All of the plates were coated with gold to prevent corrosion and to improve conductivity. Two air-breathing 2.54cm×2.54cm×1.47cm fuel cell stacks were designed and assembled for this research. The same membrane electrode assembly (MEA) with an active area of 1cm2 was tested with all of the silicon flow field plates with microchannels. The fuel cell performed well with the 20-μm width and depth flow channels (maximum power density of 65Wcm−2 or a maximum of 170mAcm−2 at 0.2V), although all of the I–V tests yielded good results for room temperature, air-breathing fuel cells. Microchannels with widths and depths from 100μm to 20μm look promising for new high-current density microelectro mechanical (MEMS) fuel cell designs.