The electrochemical nucleation of carbon in molten alkaline fluoride media is investigated using cyclic voltammetry and chronoamperometry in the 670-750 degreesC temperature range. Chronoamperometric results show that the deposition process involves progressive nucleation with diffusion-controlled growth of the nuclei, and scanning electron microscopy shows that the shape of the nuclei is hemispherical. The influence of the temperature and the overpotential on the nuclear site densities is also considered.