The novel resorcinol-formaldehyde/SiO2 (RF/SiO2) hybrid aerogels were chosen to synthesize the cubic silicon carbide (beta-SiC) nanostructures via a carbothermal reduction route. In this process, the in situ polymerized RF/SiO2 aerogels were used as both the silicon and carbon sources. The morphologies and structures of SiC nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and high-resolution transmission electron microscope (HRTEM) equipped with EDS. The effects of C/Si atomic ratios in RF/SiO2 aerogels and heat treatment temperatures on the formation of SiC nanomaterials were investigated in detail. It was shown that beta-SiC nanowhiskers with diameters of 50-150 nm and high crystallinity were obtained at the temperatures from 1400 to 1500 A degrees C. The role of the interpenetrating network of RF/SiO2 hybrid aerogels in the carbothermal reduction was discussed and a possible mechanism was proposed.