A group of women with otherwise unexplained urinary retention occurring as an isolated phenomenon have been shown to have abnormal urethral sphincters, as assessed by electromyography, transvaginal ultrasonographic volume and pressure profile. A questionnaire survey of a number of women diagnosed with the disorder showed that there was a common natural history, and from the results it was possible to build up a profile of the "typical" patient. She is likely to be between 20 and 35 years old and also to have polycystic ovaries. Before the onset of retention she is likely to have had a relatively mild voiding dysfunction, such as infrequent voiding or an intermittent stream. Commonly her first retention episode will follow a triggering event such as an operation or childbirth. The retention is unlikely to resolve but is not associated with the development of other disorders. Neuromodulation of the sacral nerves is the only intervention that has been demonstrated to restore voiding.