The migration enthalpy of monovacancies in α-Fe,H1vm, is deduced from the growth of voids during electron irradiation as studied by Kitajima and co-workers in a high-voltage electron microscope. In this wayH1vM = (1.3+0.1−0.3) eV is obtained, in excellent agreement withH1VM = (1.28±0.25) eV as deduced by Schaeferet al.from high-temperature equilibrium experiments. The disagreement betweenH1VM andH111= (0.55±0.05) eV, the activation enthalpy in recovery stage III of %aL-Fe after irradiation or cold-work, excludes the one-interstitial model but is in accordance with the two-interstitial model of point defects in metals.