Abstract: An improved, copolymer-based immunoassay system, method, and apparatus is highly sensitive and effective in accurately measuring extremely low concentrations, such as 10.sup.-6 to 10.sup.-12 grams per milliliter, of biologically active substances, such as monoclonal or polyclonal antibodies and antigens, cancer markers, proteins, bacteria, viruses, therapeutic drugs, drugs of abuse, and food and water contaminants in fluid samples. The system requires no sample preparation, and is reliable, easy to use, sufficiently low in cost to be readily usable in doctors' offices, small labs, and other low-volume facilities, but is also readily adaptable to hospital and high-volume use. The new system, method, and apparatus for agglutination immunoassay systems includes novel and coordinated carrier particle technology, light application and measurement and chemistry, coacting to provide the multiple advantages of simplicity and accuracy in use, and extreme sensitivity in application, in quantifying immunoassays.