Аннотация:The transitions of relativistic electrons in a magnetic field with the emission of an antineutrino-neutrino pair are considered. Probabilities are obtained for electron transitions to the ground state and weakly excited states. It is shown that in the case of an ultrastrong magnetic field (H≳H_0 =m ^2c^3/eħ=4.41·10^{13} G) such transitions made a considerable contribution to the total probability of the process.