The definitive identification of mycoplasmas is usually based on serological procedures, including growth inhibition (1,2), metabolic inhibition (3,4), immunofluorescence (5–7), and immunobinding assays (8–14). The technique most commonly adopted for the routine identification of mycoplasma species isolated from clinical material is, at present, the immunobinding assay involving either broth culture (12,14), mycoplasma colonies on agar plates, or the imprints of colonies (8–13). Several procedures with polyclonal or monoclonal antibodies (MAb) have been described. All these assay systems are based on the detection of mycoplasma surface antigens, which are believed to be highly specific.