A high-temperature treatment of fossil oil fly ash produced as combustion materials in oil-burning power plants is discussed with the aim of exploring the possibility of extracting vanadium compounds. As a first step, an attempt has been made to characterize the oxidation state of the vanadium in the powder, developing subsequently a thermal transformation in order to enrich the fossil oil fly ash in vanadium compounds suitable for its technological utilization. Several analytical techniques (EDS, ESCA, X-ray, atomic absorption) have been employed to characterize the vanadium content before and after various steps of a thermal treatment. The thermal treatment has been carried out with the aim of preparing higher value materials from the vanadium in the original state. A high percentage of V4C3 was obtained with the simultaneous depletion of the heavy metals present in the sample.