Gonorrhea is the most frequent bacterial infection as well as the most frequently reported venereal disease. Nongonococcal urethritis has approximately the same incidence as acute gonorrhea in cases reported by many venereal disease clinics. The relative epidemiology of the two diseases, as well as their acute and chronic manifestations in the male genital tract (urethritis, prostatitis, and epididymitis), will be briefly discussed. Resultant obstructions of the lower genitourinary tract of possible consequence to male fertility, such as urethral stricture disease and strictures of the ejaculatory ducts, are described in terms of anatomy, pathophysiology, and treatment. The postulated and demonstrable effects of infectious agents on seminal fluid and sperm are reviewed, with emphasis on the recent literature concerning Chlamydia and Mycoplasma.