Three large and well known geothermal areas at Waimangu, Waiotapu, and Waikite, together with two less well known areas at Te Kopia and Reporoa, occur in the central part of the Taupo Volcanic Zone. These areas contain a wide range of thermal discharge features. Waimangu and Waiotapu contain probably the finest, easily-accessible features still in existence in New Zealand (outside of Whakarewarewa in Rotorua), and are now protected for tourist development. The first scientific account of these features was given by Hochstetter who visited the area in 1859, but it was not until the late 1920s that any serious studies were made. Indeed, few studies have been made of these areas, except for exploratory drilling and scientific investigations at Waiotapu in the late 1950s and 1980s. The areas are of scientific importance because they are places where studies can be made of the natural variations in geothermal phenomena, uninfluenced by the effects of exploitation. Outstanding questions which remained to be resolved, prior to publication of this Special Issue, were the subsurface extent of the geothermal system(s) which feed the discharge features, the location of upflow zones, the relationships between the geothermal areas, the chemistry of the fluids, and the effects of the 1886 Tarawera eruption on the system(s).