A process for producing-vapor grown carbon fiber (VGCF) reinforced continuous fiber performs for the manufacture of articles with useful mechanical, electrical, and thermal characteristics is disclosed. Continuous fiber preforms are treated with a catalyst or catalyst precursor and processed to yield VGCF produced in situ resulting in a highly entangled mass of VGCF infused with the continuous fiber preform. The resulting continuous fiber preforms are high in volume fraction of VGCF and exhibit high surface area useful for many applications. Furthermore, this invention provides for a continuous fiber preform infused with VGCF so that the carbon nanofibers are always contained within the fiber preform. This eliminates the processing steps for isolated carbon nanofibers reported in other carbon nanofiber composite approaches and therefore greatly reduces risk of environmental release and exposure to carbon nanofibers.