INTEREST in carbon fibres1,2 has been stimulated greatly by the recent discovery of hollow graphitic tubules of nanometre dimensions3. There has been much speculation about the properties and potential application of these nanotubes4-8. Theoretical studies predict that their electronic properties will depend on their diameter and degree of helicity4,5. Experimental tests of these ideas has been hampered, however, by the lack of macroscopic quantities of the material. Here we report the synthesis of graphitic nanotubes in gram quantities. We use a variant of the standard arc-discharge technique for fullerene synthesis under a helium atmosphere. Under certain conditions, a carbonaceous deposit forms on one of the graphite rods, consisting of a macroscopic (diameter of about 5 mm) cylinder in which the core comprises pure nanotubes and nanoscale particles in high yield. The purity and yield depend sensitively on the gas pressure in the reaction vessel. Preliminary measurements of the conductivity of the bulk nanotube material indicate a conductivity of about 100 S cm-11.