Immunofluorescence detection of C. trachomatis requires trained personnel because the threshold between positive and negative reaction is not obvious. Patients antibodies must cover EB and thus prevent binding with Mab. This problems have stimulated research on Chlamydiae probes DNA hybridization technology was applied and the specificity of the detection of CT was improved. Moreover, a polymerase chain reaction amplification of a fragment of about 1,200 bp of the M.O.M.P. gene followed by restriction endonuclease digestion with selected enzymes allows differentiation of serovars. This method seems to be promising for epidemiologic studies.