The history of laboratory testing closely follows developments in the field of immunology in general. Serologic investigations were a natural outgrowth of the study of immunity, and the period from 1900 to 1950 has been called the era of international serology (1). Serology is the study of the noncellular components in the blood. At this time, attention turned to research on the production and use of serum to control disease, and several scientific institutes were created for this purpose. Many of the tests performed in today′s clinical laboratory fall into the category of serologic tests. The need to develop rapid, specific and sensitive assays to determine the presence of important biologically active molecules ushered in a new era of testing in the clinical laboratory.