Civil conflict affects the health of individuals in many countries, and draws a substantial amount of international humanitarian aid. The most widely used indicator of the effect of conflict is the rate of civilian death during conflict. We aimed to assess mortality estimates from conflicts in Sudan, Somalia, the Democratic Republic of Congo, and Afghanistan by calculating the relative risk of death during and after conflict compared with that in preconflict peacetime. Katale, in the Democratic Republic of Congo, had the highest relative risk of death during conflict (11.2 [9.1-13.8] and 103.3 [94.7-112.6], for children younger than 5 years and the whole population, respectively). Our results suggest that high rates of civilian mortality are determined more by the pre-existing fragility of the affected population than the intensity of the conflict. In many instances, a high rate of civilian deaths during conflict shows that international development aid before the conflict was grossly inadequate.