The relative efficiency of different media for the isolation of M. pneumoniae is discussed, with emphasis on the utility of SP-4 medium as a primary medium for isolation. Media available for isolation and identification of ureaplasmas are also described. Rapid methods of identification of isolated mycoplasmas are surveyed. The use and value of serologic procedures in the clinical laboratory are evaluated with particular reference to the complement fixation procedure and its value as compared to other methods. The possibilities for the development of direct antigen detection procedures for clinical use are discussed with particular reference to ELISA and other antigen capture methods. The problems that arise in susceptibility testing of isolates are raised, and a usable procedure is proposed both for minimal inhibitory concentration and minimal bacteriocidal concentration determination. A general procedure for the laboratory diagnosis of mycoplasmal infection that is adaptable to various laboratory circumstances and needs is proposed.