Detrusor underactivity (DU) is a common bladder dysfunction that causes lower urinary tract symptoms (LUTS) in both men and women. Currently DU can only be diagnosed by an invasive urodynamic test. Underactive bladder (UAB) is the symptombased correlate of DU, as is the case with overactive bladder (OAB) and detrusor overactivity (DO). The International Continence Society (ICS) consensus group has recently proposed a working definition of UAB as a symptom syndrome suggestive of DU. However, a symptom complex of UAB is shared by LUTS attributable to bladder outlet obstruction (BOO). Thus, UAB is not specific for DU, leading to difficulties in determining a therapeutic target (DU or BOO) in the initial management of UAB. Under these circumstances, a consensus group was formed under the auspices of the Japanese Continence Society (JCS) and diagnostic criteria were produced to poten