Tinnitus (chronic ringing of the ears in the absence of a sound source) is a major public health challenge affecting quality of life for millions of individuals around the world. Its principal cause (damage to the cochlea, which may be hidden and detected years after injury) appears to be increasing among youthful populations owing to exposure to recreational and occupational sounds for which current protective standards may be inadequate. And at present, there are no curative treatments for tinnitus. These facts alone, and the looming public health challenge they portend, are sufficient to spark its study. But research into the neural basis of tinnitus also addresses a fundamental question in neuroscience. If we can understand how the brain generates the sound of tinnitus, we may gain insight into the question of how the brain generates the sensation of other sounds. The papers published in this special issue (indicated in italics) address topics related to the neural basis of tinnitus, their implications for hearing, and the health challenge.