A magnetic stimulation coil arrangement comprising one or more coil windings 30 and a distortion arrangement 34 which is, in use, positioned adjacent to a rearward side of the coils 30 for distorting and focusing the magnetic field produced thereby. The distortion arrangement 34 comprising one or more ferromagnetic distortion formations arranged to form a loop. Preferably, the distortion formations are provided in the form of a discontinuous loop 34 extending between a first end and a second end and having a separation gap 48 there-between. The distortion formations 34 may additionally, or alternatively, be provided with both a first loop portion and a second loop portion. In use, the first and second loops are located adjacent the rearward sides of first and second windings respectively of a magnetic coil 30.
