The caves of the Judbarra / Gregory National Park were known to the Aboriginal tribes of the area who used them for art and ritual sites. The initial work by Northern Territory Parks and Wildlife Commission Rangers Keith Claymore and Keith Oliver was followed by the Operation Raleigh Expedition from the UK in 1990, which made the first maps of the caves. Starting in 1991 regular exploration and mapping expeditions by Australian cavers were coordinated by Top End Speleological Society and Canberra Speleological Society. The surveyed passage length of all caves in Judbarra/Gregory National Park is almost 220km and the longest single connected system is the 122km Bullita Cave System in the Central Karst Area. Studies of the geology and biology of the caves were also conducted during this time and are reported on in separate papers in this volume.