Bacteriuria is more common in females than males except in the first year of life. There is an association between circumcision status and the risk of febrile urinary tract infection (UTI) in male infants. Most UTIs in men are complicated and relate to a combination of two factors: disturbed urodynamics and invasive ability of uropathogens. A significant number of men experience UTI in association with bacterial invasion of the prostate, the seminal vesicles and the epididymis (male adnexitis). In these men, to eradicate bacteriuria antibacterial agents with adequate pharmacokinetic properties have to be used for a sufficient length of time. Non-specific urethritis, including non-gonococcal and postgonococcal urethritis, in about 50% of cases is caused by Chlamydia trachomatis and in about 5–10% of cases, by other agents such as Ureaplasma urealyticum and Trichomonas vaginalis. Examining the first-voided urine from men is as sensitive as testing a urethral swab for C. trachomatis. For chlamydial genital infections, tetracyclines, fluoroquinolones, erythromycin and the newer macrolides are suitable drugs. Azithromycin, prescribed as single-dose therapy is equivalent to 7-day course. Approximately 1% of men presenting with non-specific urethritis develop sexually-acquired reactive arthritis, one-third of these acquiring Reiter's syndrome. Studies have identified chlamydial elementary bodies in joint material in some of these patients. Placebo-controlled treatment studies have demonstrated diminished duration of active arthritis in the treatment group.