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Self-diffusion in nickel single crystals is measured between 813 and 1193 K using ion-beam sputtering as a microsectioning technique. Gaussian activity-depth profiles are observed over about three orders of magnitude in the activity decrease. The bulk diffusivities obtained from these profiles are analysed in conjunction with Bakker's high temperature data. The monovacancy contribution to the lattice diffusivity is given by Dmath image = 0.92 exp (−2.88 eV/kT) cm2/s. Preliminary isotope effect experiments are also performed at two temperatures in the high-temperature region. The results support the view that a divacancy contribution to self-diffusion exists near the melting point.