Concentrated solar radiation is used as the clean source of process heat for the production of catalytic filamentous carbon (CFC) by thermal decomposition of gaseous hydrocarbons (CH4 and C4H10) and by CO disproportionation in the presence of small metal catalyst particles. Depending on the catalyst, two different types of CFC, namely nanotubes and nanofibers, are obtained in solar experiments. Nanotubes are formed mainly using Co/MgO catalyst for CO and CH4 + H-2; nanofibers are formed mainly on Ni/Al2O3 catalyst for CH4, CH4 + H-2 and C4H10. Laboratory experiments confirm these findings. Typically, the following properties were determined by BET and X-ray diffraction for CFC samples formed under both solar and laboratory experimental conditions: the surface area is about 50-170 m(2)/g, the pore Volume is in the range of 0.4-0.8 cm(3)/g, the micropore volume is between 0.002 and 0.008 cm(3)/g, and the average pore diameter ranges between 10 and 40 nm. From these properties and from the inspection of high-resolution transmission electron micrographs we conclude that CFC with well-defined morphology can be produced using concentrated solar radiation.