Direct methanol fuel cell operation with uniaxially pre-stretched recast Nafion membranes (draw ratio of`4) was investigated and compared to that with commercial (un-stretched) Nafion (R). The effects of membrane thickness (60-250 mu m) and methanol feed concentration (0.5-10.0 M) on fuel cell power output were quantified for a cell temperature of 60 degrees C, ambient pressure air, and anode/cathode catalyst loadings of 4.0 mg cm(-2). Pre-stretched recast Nafion (R) in the 130-180 I.Lm thickness range produced the highest power at 0.4V (84mWcm(-2)), as compared to 58 m W cm(-2) for Nafion (R) 117. MEAs with pre-stretched recast Nafion (R) consistently out-performed Nafion (R) 117 at all methanol feed concentrations, with 33-48% higher power densities at 0.4V, due to a combination of low area-specific resistance (the use of a thinner pre-stretched membrane, where the conductivity was the same as that for commercial Nafion (R)) and low methanol crossover (due to low methanol solubility in the membrane). Very high power was generated with a 180 mu m thick pre-stretched recast Nafion (R) membrane by increasing the cell temperature to 80 degrees C, increasing the anode/cathode catalyst loading to 8.0mg cm(-2), and increasing the cathode air pressure to 25 psig. Under these conditions the power density at 0.4 V for a 1.0-M methanol feed solution was 240mWcm(-2) and the maximum power density was 252 m W cm(-2). (C) 2008 Elsevier B.V. All rights reserved.