Novel magnetic assay methods and systems. According to a preferred embodiment, a chromatographic medium is provided that is designed to be contacted with a test solution having activated magnetic particles such that the solution flows bilaterally thereacross. A magnetic field, generated by a magnet or electromagnet, is selectively applied to the medium which causes the charged particles to become substantially bound at a site on the medium specified by the position of the magnet, to thus form a captured line or zone. In one preferred embodiment, the magnetic field is applied at the site on the medium at which the test solution is contacted. The assay is multi-configurable and can be modified to suit a particular immuno-separation procedure or application.