Production of nanotubes of carbon or of other inorganic material by moving a carbon-containing substrate (8), such as a tape or belt of carbon fibres, within a reaction chamber (1) either through an electric arc in a gap between two electrodes (2, 3) or adjacent an electrode so that an electric arc exists between the electrode and the substrate, to cause the nanotubes to form on the substrate (8). The method enables the continuous or semi-continuous production of nanotubes. Preferably, the process is carried out at atmospheric pressure and nanotubes of high purity are produced.