The use of internal reinforcement in pulsed field magnets is shown to be most efficient in terms of pulse duration and peak field. However, it requires that the mechanical properties of the reinforcement are matched to those of the conductor. The principles for the use of filaments of pearlitic steel as internal reinforcement are studied as well as the practical implications regarding the manufacturing of the magnets. For this application, filaments with a rectangular cross section with dimensions of some tenths of a millimeter are produced that have tensile strength up to 3.0 GPa. The rectangular cross section allows one to obtain a high packing factor and the average strength of the reinforcement is therefore competitive to fibre reinforcements such as glass fibre and carbon fibre. A detailed analysis of the properties of the pearlitic filaments will be presented together with experimental evidence resulting from magnet testing.