The distribution of transgressive coastal sand dunes in eastern New South Wales and Queensland is summarised and the factors involved in transgressive dune initiation are reviewed. On the basis of radiocarbon and pedological evidence, it is suggested that episodes of transgressive dune instability have been synchronous over large areas. Widespread sand blowing appears to have taken place in the early Holocene between 9,000 and 7,000 years ago. Instability was also widespread between 3,500 and 2,000 years ago and within the last thousand years. Possible causes of dune instability are considered.