Non-gonococcal urethritis (NGU) is caused by Chlamydia trachomatis in 11–50% of cases, but Mycoplasma genitalium is being increasingly recognized as a common cause. Mycoplasma genitalium is not as well understood, and experience with treatment is limited; however, antibiotic resistance is already a problem. Asymptomatic in up to 20% of men, symptoms include dysuria and urethral discharge. Mucopurulent cervicitis is the female equivalent, but is less well defined. This chapter describes the aetiology, clinical features, complications, and investigations and management of NGU, and mucopurulent cervicitis. Management of recurrent and persistent urethritis is also covered, including a separate section for diagnosis and management of Mycoplasma genitalium.