Abstract: An assembly for monitoring torsional loading of a drive shaft comprises a magnetic-field generator juxtaposed to a cylindrical body of magnetostrictive material rigidly surrounding the shaft, the body being in the form of a thin foil attached to the shaft via a layer of magnetically insulating material, or a sleeve attached to the shaft by at least two spaced brackets or an outer layer of the shaft specially treated to have a homogeneous magnetic permeability in an unstressed state. A pick-up or magnetic-field sensor is juxtaposed to the body or sheath for detecting differential changes in the magnetic permeability thereof, the pick-up advantageously being connected to a demodulator which extracts a signal whose polarity is determined by the direction of loading of the shaft.