Porous　silicon　carbide/silicon　nitride　(SiC/Si3N4)　composite　ceramics　with　flexural　strength　of　78　MPa,　fracture　toughness　of　1.68　MPa　m(1/2),　and　porosity　up　to　63%　were　obtained　by　gel　casting　and　two-step　sintering　using　commercial　phenolic　resin　as　carbon　source.　Thermogravimetric　analysis　(TGA),　Fourier　transform　infrared　spectroscopy　(FTIR),　scanning　electron　microscopy　(SEM),　X-ray　diffraction　(XRD),　transmission　electron　microscopy　(TEM),　and　three-point　bending　methods　were　employed　to　characterize　and　analyze　the　microstructure　and　basic　mechanical　performance　of　the　porous　ceramics.　The　polymer　was　proved　to　be　an　effective　source　that　could　provide　free　carbon　for　fabrication　of　the　SiC　nanoparticles　by　in　situ　reaction　with　Si3N4　and　SiO2.　Sizes　of　the　formed　SiC　particles　were　in　the　range　of　50-300　nm.　Low　green　density,　significant　weight　loss,　and　little　shrinkage　led　to　high　porosity.　High　aspect　ratio　of　beta-Si3N4,　uniform　porous　distribution,　and　formation　of　proper　amount　of　SiC　particulates　were　the　main　reasons　for　good　mechanical　performance.　However,　only　a　limited　amount　of　polymer　additions　had　these　beneficial　effects.　Excessive　additions　could　cause　agglomeration　for　residual　carbon　and　inborn　SiC,　hence　becoming　fatal　flaws　for　the　materials.　(C)　2004　Elsevier　B.V.　All　rights　reserved.