[en] Electron captures and neutron emissions by atomic nuclei in dense matter are among the most important processes governing the late evolution of stars. Not only do these processes limit the stability of massive white dwarfs, but also lead to the neutronization of matter in the interior of neutron stars. Although these processes have been known for a long time, most studies have focused on nonmagnetized matter. On the other hand, some white dwarfs and neutron stars are endowed with very strong magnetic fields, of the order of 10"9 G and 10"1"5 G respectively. As a matter of fact, much stronger fields may potentially exist in their interiors. In this paper, we review our recent studies of the role of a strong magnetic field on the onset of electron captures and neutron emissions in dense stellar matter. (author)