Self‐diffusion in graphite was measured over the temperature range from 1835°C to 2370°C by observing the penetration of C‐14 tracer initially applied to one end of a graphite rod.The experimental data were found to be in agreement with a diffusion mechanism consisting of concurrent volume and grain boundary processes. Activation energies for both processes (EVandEB) could not be uniquely obtained from the data, however. An independent determination of either is required in order to evaluate the other. On the basis of recent theoretical work,EVmay be taken to be 90 kcal/mole. From the present experiments and the above value ofEV, the activation energy for grain boundary diffusion,EB, is calculated to be 75.4 kcal/mole.