Silicon carbide (SiC) porous substrates are prepared by pressureless sintering of SiC powders under an inert atmosphere of argon. The porous SiC substrates were characterized by measuring their porosity, pore size distribution, surface characteristics, and structure. Their transport characteristics were investigated using N-2 and He as the test gases. Three different starting powders and four different sintering aids, Al2O3, B4C, carbon black, and phenolic resin, either by themselves or in combination, were investigated in terms of their ability to prepare good quality substrates. It was found that the porosity, pore size distribution, and transport characteristics of the resulting SiC-sintered bodies depend on the nature of the original. powder, the particle size in the green SiC samples, and the type and molar ratio of the sintering aid utilized. Depending on the preparation technique, both mesoporous and macroporous materials could be prepared. These supports are currently utilized for the preparation of microporous membranes.