Polycrystalline nickel (purity 99.9% was either cold-rolled below room temperature or quenched from 1000 °C. The recovery of the electrical resistivity was studied between 0 °C °C and 300 °C. After cold-work two separate recovery processes were found in this temperature range (stage III near 80 °C. stage IV near 250 °C with activation energies of 1.09 ± 0.05 ev and 1.55 ± 0.10 ev. respectively. After quenching from 1000 °C only stage IV was present (maximum of the recovery rate near 270 °C, activation energy about 1.5 ev), whereas stage III was not observed. On account of the present results and other available data free interstitial migration is attributed to stage III and the migration of single vacancies to stage IV. We estimate that the energy of formation of single vacancies in nickel is 1.3 — 1.4 ev, and that the volume increase per vacancy is 0.82 atomic volumes.