The synthesis and characterization of radially-aligned carbon filaments (RACF) produced from light hydrocarbons are reported. RACF grow spontaneously on the surface of a resistively heated (1100-1700 degrees C) carbon yarn exposed to C1-C3 hydrocarbons (methane, ethylene, propane) as carbon precursors. The diameter of the RACF depends on the temperature, exposure time, nature of hydrocarbon, and it ranges from 700 nm to 40 microm, with the length of the carbon filaments reaching up to 800 microm. The morphology and microstructure of the produced carbon filaments were analyzed by a number of materials characterization techniques, and it was shown that they feature a tree-ring type structure made of turbostratic carbon layers. RACF are characterized by the presence of cracks (50-100 nm in width) between the consecutive "tree-rings" and a crenulated structure of the exterior surface of the filaments. The RAFC growth mechanism is yet to be fully understood. Pros and cons for the catalytic versus non-catalytic growth models for the RACF are discussed in the paper.