A system for monitoring the condition of a conveyor belt having magnetically permeable cords, has a magnetic field generator for generating a magnetic field to magnetize the cords, in use, a magnetic field sensing unit for sensing the magnetic field provided, in use, by the cords, the sensing unit comprising an array of spaced magnetic field sensors, the spacing of the sensors being sufficiently close to discriminate between adjacent cords. The spacing of the sensors depends on the spacing of the cords, and may be less than half the spacing between cords of a conveyor belt. The sensors may be direction sensitive and the sensors may be oriented in more than one direction, to sense the perpendicular and other components of the magnetic field.