Chemiluminescence immunoassay is now established as one of the best alternatives to conventional radioimmunoassay for the quantitation of low concentrations of analytes in complex samples. During the last two decades the technology has evolved into analytical procedures whose performance far exceeds that of immunoassays based on the use of radioactive labels. Without the constraints of radioactivity, the scope of this type of analytical procedure has widened beyond the confines of the specialist clinical chemistry laboratory to other disciplines such as microbiology, veterinary medicine, agriculture, food and environmental testing. This is the first work to present the topic as a subject in its own right.