Acute urinary retention (AUR) is a common presentation to emergency departments. This article updates the reader on the appropriate management, investigations and guidelines for AUR. It looks at the mechanism of normal micturition and describes the theories of AUR. It outlines urethral catheterization techniques for difficult cases, reviews suprapubic catheterization procedures and describes the management of AUR in polytrauma. Although emergency management is by bladder drainage, key points in the history and examination may expose significant, latent pathologies.