Behavior of dislocations in metals exposed to fast neutron irradiation and subjected to alternating stresses is investigated. Under these conditions, radiation annealing as well as multiplication of linear dislocations were observed. A theoretical model of dislocation climb is proposed, and a physical explanation of radiation annealing of dislocations is given in terms of this model. A mechanism for dislocation multiplication is also proposed. Behavior of dislocations in irradiated and unirradiated metals in annealing in the electron microscope is also investigated.