Underactive bladder (UAB) and detrusor underactivity (DUA) are common, aging-related, multifactorial conditions• Aging may be an etiological factor, but concomitant disorders may aggravate aging-induced reduction in bladder structure and function • Bladder outflow obstruction, diabetes mellitus, neurogenic disorders, and ischemic bladder dysfunction, are often associated with UAB/DUA• Impaired detrusor contractility has been regarded as a major etiologic factor of UAB/DUA, but disturbances of bladder sensory afferents and the central nervous system control of micturition and changes in efferent neurotransmission may be as important • Chronic bladder ischemia and resultant oxidative stress may cause detrusor overactivity progressing to DUA and inability to empty the bladder.