A progressive, incurable disease of little ponies. All pony types are affected, and the disease is more common in the inland Dusts than in other regions of the Isle of Yore. Zebras and zonies are rarely affected.

The feature for which the disease is named is a hoof disease that eventually leaves sufferers unable to walk without assistive devices, but it is ultimately a fatal disease of the hollow organs, progressing rapidly once symptoms of visceral involvement begin. (This does not happen to all victims, though, at least not by the time they have died of unrelated causes.) Opinions on whether hoofrot is a contagious disease have varied over the centuries - most eminent physicians believe that it is not contagious, or that it is contagious only to a small minority of susceptible individuals, but due to caution and tradition, most sufferers are still isolated. (Typically in the village of Slag Hollow in the Eastern Dusts.) The disease was apparently unknown in the Golden Age, appearing during the Dark Age at the latest. Its course is thought to be slowed by frequent bathing, which is only partially effective and is expensive. Oiling the hooves is another treatment, which reduces the progression of the hoof disease, but does not reverse existing hoof lesions or significantly reduce the chances of visceral disease. Magical cures of hoofrot are occasionally reported, but most healers do not give much credence to such claims.