Membrane distillation (MD), a thermally-driven membrane separation process has been widely studied in recent years and the membrane properties are known to have significant effect on the performance of the MD process. This paper studied the microstructure of PTFE membranes from three different sources for MD application. The parameters investigated include pore size, thickness, porosity and tortuosity. Non-supported membranes were also tested for comparison. The experimental results for different pore size, thickness, porosity, tortuosity and support materials in direct contact membrane distillation (DCMD) were compared with the theoretical flux simulated from the Schofield model using Polymath NLE solver. The temperature polarisation coefficient was also determined to establish the relationship between the membrane microstructure and performance. The results indicated that the structure and porosity of support materials play important roles in determining the performance of DCMD. Higher fluxes and lower temperature polarisations were observed over membranes with large pore size, low thickness, high porosity and low tortuosity. Membrane porosity, pore size and the presence of support materials were found to have significant effects on flux and temperature polarisation. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.