an immunoscintillating composition and method of radioimmunoassay is disclosed whereby polymer coated paramagnetic particles and binding agent such as an antibody are associated by chemical or physical means to provide solid scintillating immunoadsorbent particles which are paramagnetic . these particles are capable of selectively binding or retaining radioactive or labeled antigens or ligands and transmitting radioactive energy to a phosphor or photon emitting substance that is bound by chemical or physical means to the particles . upon binding of the antigens or ligands to the surface of the particles the particles are separated from the unbound components in solution by application of a magnetic field . the luminescence emitted by the phosphor which is attached to the magnetically separated particles is measured by a scintillator counter and is directly proportional to the radioactive energy released by the labeled antigen bound to the antibody . upon completion of the measurement the paramagnetic particles can be magnetically separated and the labeled antigens or ligands removed for further analysis and the particles recycled for use in other assays .