While there have been many attempts to calculate pre-contact Aboriginal population sizes for Tasmania, estimates have varied from as little as 800 to as many as20,000. We adapt a technique employed by Noel Butlin to model Australian continental populations in 1788 to the peculiar circumstances of Tasmania. We conclude that higher, rather than lower, pre-contact populations are likely. While the direct and indirect consequences of conflict were a serious contributor to the collapse in population, introduced disease played a significant role. This included sexually transmitted disease (a cause of declining fertility), as well as pulmonary disorders and crusted scabies.