Synthesis of filamentous carbon through the decomposition of chromium carbide was studied employing hydrothermal technique in the pressure and temperature range of 100-200 MPa and 350-800 degrees C respectively. It was found that chromium carbide dissociates into chromium oxide in the presence of water at temperature < 400 degrees C. But, the formation of free elemental carbon as filamentous particles was noticed in the presence of organic compounds at temperatures above 600 degrees C. The organic compounds are known to dissociate to C-O-H supercritical fluids under hydrothermal condition. The supercritical fluids generated by the dissociation of organic compounds have great influence on the decomposition of chromium carbide. The scanning electron microscopic (SEM) studies of the experimental run products show that the fibrous or filamentous form of carbon was found with a few spherical shaped carbons, in the chromium carbide-organic compound runs. These carbon particles were solid curved filaments with a mean diameter of 50-100 nm. Micro Raman spectroscopic studies show that the filaments have sp(2)-hybridized carbon atoms.