Non-gonococcal urethritis and its counterpart in women have become the most frequent genital infection worldwide. As Chlamydia trachomatis is the major causative agent interest has focused on this bacterium. While genital chlamydial infection in men often is manifest the opposite holds true for women. Major complications such as pelvic inflammatory disease can nevertheless turn up. Therefore efficient diagnostic tools are badly needed. If tissue culture procedures are not available direct specimen tests can be performed using fluorescence labelled monoclonal antibodies. For therapy tetracyclines and erythromycin are still the drugs of choice although the cure rates are not totally acceptable. Therefore evaluation of the new quinolones deserves interest.