Armed conflict causes an enormous amount of death and disability worldwide. It destroys families, communities and cultures. It diverts scarce resources. It disrupts the societal infrastructure that supports health. It forces people to leave their homes and become internally displaced persons or refugees who have fled to other countries. It violates human rights. It promotes violence as a means to resolve conflicts and it degrades the environment. Armed conflict has an even more profound effect on low- and middle-income countries. Health professionals can play important roles in minimising the adverse consequences of war and in preventing war itself.