Qualitative and quantitative analytical procedures that rely on the ph
enomenon of chemiluminescence are now widely used in clinical biochemi
stry, cell biology, and molecular biology. It is a little more than 15
years since the appearance of reports of immunoassays based on chemil
uminescent signal detection. Since then, the inherent advantages of th
ese non-isotopic labels have combined with other technological improve
ments and sophisticated instrument development to provide immunoassays
with a level of analytical performance that would have been difficult
to imagine 15 years ago. This review highlights the main factors whic
h I believe have contributed to this remarkable progress in high sensi
tivity analysis.