Abstract In order to obtain information on the microstructural state of a material by means of non-destructive methods, the Barkhausen noise resulting from the irreversible movement of the Bloch walls in a ferromagnetic material was used. The microstructural and magnetic investigations were done on different microstructural conditions of the steels 22 NiMoCr 3 7, X 20 CrMoV 12 1 and X 20 Cr 13. The results of the nondestructive magnetic measurements show that the Barkhausen noise is suitable for distinct separation of material conditions, whose structures can be distinguished by light optical microscopy. Furthermore, separation of material conditions, which in practice cannot be distinguished by light optical microscopy or by means of their hysteresis curves, is possible. Relating the measured differencies in the Barkhausen noise to the microstructural parameters, determined by transmission electron microscopy, one recognizes that changes in the density and arrangement of the dislocations are the main reason for the observed behavior. Residual stresses can also be important.