We present the updated International Union against Sexually Transmitted Infections (IUSTI) guideline for the management of non-gonococcal urethritis in men. This guideline recommends confirmation of urethritis in symptomatic men before starting treatment. It does not recommend testing asymptomatic men for the presence of urethritis. All men with urethritis should be tested for Chlamydia trachomatis and Neisseria gonorrhoeae and ideally Mycoplasma genitalium using a nucleic acid amplification test (NAAT) as this is highly likely to improve clinical outcomes. If a NAAT is positive for gonorrhoea, a culture should be performed before treatment. In view of the increasing evidence that azithromycin 1 g may result in the development of antimicrobial resistance in M. genitalium, azithromycin 1 g is no longer recommended as first line therapy, which should be doxycycline 100 mg bd for seven days. If azithromycin is to be prescribed an extended course of 500 mg stat, then 250 mg daily for four days is to be preferred over 1 g stat. In men with persistent NGU, M. genitalium NAAT testing is recommended if not previously undertaken, as is Trichomonas vaginalis NAAT testing in populations where T. vaginalis is detectable in >2% of symptomatic women.