Male prison rape and sexual assaults remains a serious and sensitive issue in many countries. Human rights groups claim that sexual assaults among male prisoners have reached pandemic proportions and need to be stopped. Researchers for many years have studied the causes of male sexual assault in prison and offered numerous recommendations on its prevention. Few, however, have presented evidence for a decline in male prisoner sexual assaults and investigated the reasons for the decline. This article provides evidence from population-based surveys of a steady decrease in male prisoner sexual assaults in New South Wales (NSW) between 1996 and 2009. The authors conducted in-depth interviews with former and current inmates, and using a "systems" approach they discuss the complexity of sexual assaults in prison, incorporating a multiplicity of perspectives. In particular, they bring together different sources of data and discuss this in relation to changes in power structures and control in a modern prison, the attitudes of older and younger prisoners, the concept of "duty of care," introduction of prison drug programs, and prisoner attitudes toward gender and sexuality. In anthropology, the term "system" is used widely for describing sociocultural phenomena of a given society in a holistic manner without reducing the complexity of a given community. (Contains 2 tables.)