While most practitioners are familiar with overactive bladder, the converse condition of underactive bladder has generally remained far below the radar. As a consequence, there is still a lack of empirically validated treatments and effective treatment strategies. This is a matter of concern, especially as the burden of the condition is expected to rise in line with the aging of global populations. The Underactive Bladder is a major step forward in raising awareness, exploring best practices in patient care, and searching for future therapies. It will be invaluable for urologists, geriatricians, other specialists, researchers, and nurses.