The relationship between immigration and crime rates has long been a topic of robust debate in criminology and sociology, especially for scholars of the United States. Researchers in those fields have highlighted divergent factors to explain high arrest rates including the presence of ethnic gangs, media reporting, racial profiling, over-policing of immigrant communities, and wider issues of social dislocation brought about by migration. By contrast, historians have given little consideration to the topic. This lack of historical investigation is particularly curious in studies of Australia's post-war immigration given the political importance of the issue at the time. Immigration and criminality -or more precisely, whether immigrants committed more crime or worse crimes than the Australian-born population -became a prominent topic of media coverage and political interest in the early 1950s. In fact, the question of migrants' criminality was so important that it was the subject of the first research inquiries ever ordered by the Department of Immigration. Our article examines this research, explaining the impetus for the inquiries, their findings, and their historical significance. We conclude by outlining how this topic can illuminate new areas of inquiry in immigration history.