Activation energies for high temperature creep determined under constant normalized stress, σ_c⁄E_T, agreed with activation energies for self-diffusion both in paramagnetic and ferromagnetic temperature regions of alpha iron. Activation volumes for creep deformation determined by stress relaxation tests during creep ranged from 5×10² b³ to 1.4×10³ b³. An analysis of the obtained results suggests that creep deformation of alpha iron is determined by the diffusion-controlled motion of screw dislocations which contain super-jogs. The height of the jogs was estimated at about 10b to 20b under different creep conditions. The super-jogs are supposed to be formed by the accumulation of elementary jogs produced on dislocations when the dislocations are pulled out from sub-boundaries. The dislocation densities and their stress dependence obtained on the basis of the motion of super-jogs were in good agreement with the results reported so far.