Abstract: A device for treating fluids passing therethrough with a pulsed DC magnetic field includes a cylindrical conduit of nonmagnetic material in which there is captively held a plurality of adjacently contacting solid ferromagnetic but unmagnetized spheres. At opposite ends and surrounding the cylindrical conduit is a pair of annular pole pieces made of a ferromagnetic material between which there is circumferentially wound an activating coil supplied with pulsed DC from a power supply. The interrupted DC field provides, in connection with the pole piece and spheres, a tortuous path through the treating device where the magnetic field is concentrated at the nodes defined by the pole pieces and the spheres through which the magnetic flux path is completed from pole piece to pole piece. In the preferred embodiment the device is employed for the magnetic treatment of water passing through the cylindrical conduit.