Publisher Summary This chapter reviews the current status and evaluation of the newer diagnostic methods for the measurement of a specific antibody in the infection. The discussion also covers the advantages of various antigen detection techniques in providing early diagnosis of infection. The problem in establishing a role for mycoplasmas in human sexually transmitted diseases has always been complicated by the commensal mycoplasma flora in the normal human urogenital tract. The development of effective tests has been hampered by two major constraints: (1) confirmation by culture of the organism is lengthy and difficult, and (2) serodiagnosis by the commonly used complement fixation test is slow. Serodiagnosis falls short of detecting all culture-positive patients. Thus, both culture and serodiagnosis are too slow to direct early clinical intervention. Despite the limitations, the routine laboratory diagnosis of Mycoplasmapneumoniae infection often relies on serodiagnosis alone, principally by complement fixation or, more recently, on enzyme immuno assay (EIA) techniques or agglutination of antigen-coated particles. The chapter presents the three categories of tests in detail. These comprise direct detection of the organism by culture, detection of cellular components, and quantification of the non-specific and specific immunological responses of infected individuals.