The dependence of the dislocation stopping force on the dislocation velocity and the magnetic field intensity in a normal metal at low temperatures is investigated. It is shown that the dependence of this force on the dislocation velocity is a nonmonotonic function with a local minimum and maximum. The positions of the maximum and minimum of the stopping force are, respectively, independent of and dependent on the strength of the magnetic field. Dislocation motion is unstable in the velocity range where dF∕dv<0, F and v being the dislocation stopping force and velocity, repectively.