ABSTRACT During the 1999 community survey of Australian tree-kangaroos by the Tree Kangaroo and Mammal Group of the Atherton Tablelands, the well-known naturalist, John Young, submitted a detailed account of watching a tree-kangaroo for half an hour in the Iron Range rainforest of Cape York Peninsula in 1979. At the time this was treated by hard-nosed scientists as “needing confirmation”, particularly as numerous earlier collecting expeditions had worked the area without the hint of a tree-kangaroo. John's report triggered a flurry of interest and has resulted in the collation of numerous “sightings” from the Peninsula and some targeted searches for the animal, but as yet no concrete evidence. So does the animal exist? Tantalising leads, but no hard evidence, have been found for the occurrence of tree-kangaroos in the region. We discuss the possibility that such a creature exists and what might be necessary to find it, and if it does occur what level of evidence is required.