Sir William Osler, in his final published lecture, The Evolution of Modern Medicine, discussed with great optimism the emergence of preventive medicine. He marvelled at the successful public health campaigns against malaria and yellow fever that decreased morbidity and mortality by "up to an order of magnitude". Since early in the last century, scientific data have correlated clinical illness with social behaviours and public health advocates have pursued safety legislation. Most recently, public health measures have legally obligated drivers to fasten their seatbelts and severely restricted smoking. Physicians have now begun to look more closely at another social factor leading to significant clinical morbidity: violence.

Recent research has changed our perception of violence. In 1985, William Foege, then Executive Director, The Task Force for Child Survival and Development, noted that violence was largely viewed as law enforcement or welfare problem until the early 1980s. A recent literature review tallied the most common types of violence discussed in the public health context. Youth and gang violence, gun violence, and domestic violence topped the list. A third of the reviewed articles justified the role of public health in preventing violence by arguing that violence is a pervasive threat. This argument invokes one of preventive medicine's main tenets: to prevent population exposures that can inflict injury and death.

The articles in this issue explore the myriad ways in which violence results in injury and death. Salmaan Keshavjee and Mercedes Becerra link the current tuberculosis epidemic in Tajikistan to the country's civil war and separation from Russia. Sheri Fink describes the conflicts of interest faced by humanitarian aid physicians trying to mitigate the violence in the war in Kosovo. Howard Spivak, Katherine Christoffel, and Martha Witwer discuss the tragic consequences of youth violence in the United States from clinical and epidemiological perspectives. Brian Phelps addresses physicians' failure to properly screen patients for domestic violence. The authors clearly envision violence as the disease, but how can such a disease be cured?

Preventive medicine transformed the role of the physician from individual healer to caretaker for the public's health. Osler calumniated society's failure to enact preventive health measures against the unsanitary conditions conducive to typhus. But a mere bacterium causes typhus, while complex and deeply entrenched societal and governmental attitudes, such as fear of and hostility toward ethnic groups and the right of citizens to bear arms, contribute to violence and its terrible sequelae. Such causative agents have proved far harder to dismantle than a simple package of protoplasm. Osler listed the tools of preventive medicine in his 1913 lecture—"education, organization, cooperation. "Perhaps information in the following articles will help hone them against violence.