The low frequency internal friction (Q-1) of pure iron wires in a d.c. magnetic field increasing with a constant rate (H = const) was studied by a torsion pendulum a room temperature. It was found that Q-1 is composed of a static part Q0-1 (at H=0) and a dynamic part Qm-1 (at H≠0) which is viscoelastic type. The values of Qm-1 are independent of the strain amplitude Aε (in the range of 10-6 to 10-5), increase with the increase of H/ω and drop almost down to the ualues of Q0-1 when H changes suddenly from some ualue to zero. The behaviour of the static part is analogous to that of the resonance damped model of dislocation. The Qm-1-H curves of prestrained specimens are lower than those of annealed Ones and their peaks shift to higher magnetic field.