Health professionals, through their knowledge of medical ethics, public health models, and direct advocacy may suggest treatment of the vexing new problems of the 21st century. The evolving concept of Peace through Health encapsulates such activities, and Croatian Medical Journal's activities in the 1991-1995 war in Croatia is one example of such work. The Responsibility to Protect report, on the duty of the international community to prevent genocide and ethnic cleansing, shows the congruence of medical ideas with the domain of international affairs. Collateral Damage, a report on potential health consequences of war on Iraq, is a recent example of the increasing involvement of physicians in the direct conduct of world affairs. Prevention and healing on a global scale require clear ethical principles for action, just as they do in the personal practice of medicine.