Both common pathogens and unconventional, fastidious bacteria, viruses, parasites, and fungi are causative agents in male urethro-adnexitis and in female acute urethral syndrome. Uropathogens, Neisseria gonorrhoeae, Treponema pallidum, Mycobacterium tuberculosis, Chlamydia trachomatis, Mycoplasma spp., Haemophilus ducreyi, Calymmatobacterium granulomatis, Gardnerella vaginalis, anaerobic bacteria, Herpes simplex virus type II (HSV II), papillomaviruses (HPV), Trichomonas vaginalis and Candida spp. must be considered. The various diagnostic procedures and criteria applied for aetiological classification in cases of balanitis, urethritis, prostatitis, epididymitis, orchitis, and acute urethral syndrome are reviewed and evaluated.