Electrospinning of m-aramid in dimethyl acetamide/LiCl solution was investigated to develop thermo-resistant nanofibrous membranes for breathable waterproof materials. The m-aramid nanofibers were continuously generated and densely mounted to the membrane without the blockage of the spinning tip during electrospinning. In order to obtain the electrospun m-aramid nanofibers with different fiber diameters, the polymer concentration in the solution and the spinning distance were varied. Electrospun m-aramid nanofibrous membranes of various fiber diameters and thicknesses were prepared, and then compared with two commercial expanded polytetrafluoroethylene (ePTFE) membranes with respect to water vapor permeability and pore size. The m-aramid nanofibrous membrane showed a good water vapor permeability that satisfied the criterion of a breathable membrane, higher than those of the ePTFE porous membranes. Therefore, m-aramid nanofibrous membrane with thermal and mechanical resistance has great potential for breathable waterproof materials and filters. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41515.