From quenching experiments the activation energy for vacancy formation in high purity platinum is found to be 1.20±0.04 ev. Annealing behavior after quenching is studied. First‐order annealing is found when the concentration of quenched‐in defects is low; the migration energy turns out to be 1.48±0.08 ev. The annealing kinetics are not simple if the quenching temperature is high and the concentration of defects at least 10−4.