Urinary retention is the inability to voluntarily void urine. This condition can be acute or chronic. Causes of urinary retention are numerous and can be classified as obstructive, infectious and inflammatory, pharmacologic, neurologic, or other. The most common cause of urinary retention is benign prostatic hyperplasia. Other common causes include prostatitis, cystitis, urethritis, and vulvovaginitis; receiving medications in the anticholinergic and alphaadrenergic agonist classes; and cortical, spinal, or peripheral nerve lesions. Obstructive causes in women often involve the pelvic organs. A thorough history, physical examination, and selected diagnostic testing should determine the cause of urinary retention in most cases. Initial management includes bladder catheterization with prompt and complete decompression. Men with acute urinary retention from benign prostatic hyperplasia have an increased chance of returning to normal voiding if alpha blockers are started at the time of catheter insertion. Suprapubic catheterization may be superior to urethral catheterization for short-term management and silver alloy-impregnated urethral catheters have been shown to reduce urinary tract infection. Patients with chronic urinary retention from neurogenic bladder should be able to manage their condition with clean, intermittent self-catheterization; low-friction catheters have shown benefit in these patients. Definitive management of urinary retention will depend on the etiology and may include surgical and medical treatments.