After pointing out the epidemiological significance of sexually transmitted diseases, the authors report results in 100 male patients given doxycycline polyphosphate during 2 weeks for urethritis. Ten patients had post-gonococcal urethritis and twenty others had persistent urethritis afer a first treatment had failed. The association Chlamydia trachomatis-Staphylococcus albus was the most common bacteriologic finding. Staphylococcus aureus and Neisseria gonorrhea were demonstrated in 24 and 12 cases respectively. Ureaplasma urealyticum was found in only four instances. Clinical and bacteriological results show that doxycycline polyphosphate was effective in 92 out of 100 cases. Circumstances of the eight failures are analyzed specifically. Clinical tolerance was excellent in every case. Following confrontation with recent data from the literature, these results lead the authors to conclude that gonococcal and non-gonococcal urethritis is an indication of choice for doxycycline polyphosphate.