Reports coming from Central Australia draw attention to mental instability in the Aborigines who live between Hart Range and Lake Nash near the Queensland border (Fig. 1). Well-informed persons—welfare officers, nursing sisters, an aerial medical officer (“flying doctor”) and cattle station managers—are firmly of the opinion that these Aborigines show an undue amount of instability and frank mental illness. Furthermore, South Australian mental hospital records reveal that in recent years, many Aborigines of this region have been referred to Adelaide for treatment of unusual psychoses. Statistics of the sort available in more settled areas are lacking. There is no local psychiatric service to keep a register of disorders occurring in this population. But the local impression of mental instability is strong and the questions it raises are clearly important. Is there a localized instability in Central Australia ? If so, what is its distribution? What is its nature? Is its cause to be found in constitutional peculiarities of the people ? Or in environmental stresses that they are undergoing in their cultural transition ?