Impairment of bladder emptying may manifest as urinary retention, and be either acute or chronic. The underlying causes of urinary retention may be either structural or functional. Urinary retention in young women in whom no urological, gynecological or neurological abnormality can be identified presents a diagnostic dilemma. This chapter provides the main basis for understanding urinary retention in young women with Fowler's syndrome (FS). Although an early study of the effect of injection of botulinum toxin into the striated urethral sphincter failed to restore voiding in women with FS, there is some evidence that this is an intervention worth revisiting. Sacral neuromodulation (SNM) restores voiding in FS is well established, its long-term efficacy has been shown to be greatest in women with FS, and furthermore people now have a scientific basis for understanding how it works in this condition.