Bladder-wall-thickness (BWT) ultrasound assessment in lower urinary tract conditions has been studied extensively for the last 30 years. There is some evidence that it may have diagnostic utility in detrusor overactivity (DO). The cutoff value for BWT for diagnosing DO is still a matter of debate, with different studies using different values. Transvaginal scanning is the most accurate route of measuring BWT, with excellent interobserver variation and reproducibility. There is still ongoing evaluation of bladder ultrasound and its place in the investigation of overactive bladder symptoms.