Cryptococcosis is a systemic infection caused by the yeast, C. neoformans. The natural reservoirs for C. neoformans are soil and avian feces. Inhalation of yeast cells may lead to a lung infection and possibly disseminated disease. Patients often present with devastating debilitation, especially those with an immunosuppressive syndrome. Because C. neoformans has an unusual affinity for central nervous system tissue, rapid and early detection is essential. In 1963, Bloomfield reported detection of cryptococcal polysaccharide (CPS)antigens in serum and CSF of patients with cryptococcosis. In further testing, investigators reported false-positive reactions in the serum of patients with rheumatoid factor. In 1983, Stockman and Roberts introduced an enzymatic method incorporating protease to eliminate interference factors (e.g., rheumatoid factor) in serum. Such factors also include immune complexes, which have been shown to mask CPS antigen and prevent its recognition by sensitized latex particles. Since then, latex agglutination has been found to be a specific and sensitive method for rapid detection of CPS antigen in serum and CSF.