During the 100 days which followed the assassination of the Presidents of Rwanda and Burundi on 6 April 1994 up to a million people, mainly members of the Tutsi tribe, were massacred in Rwanda. This paper describes the consequences and provides a personal view regarding the factors that, taken together, explain this awful act of genocide. Factors that are considered include population pressure in a densely populated country, conspiracy by members of a ruling élite whose power was crumbling, brutalization and indoctrination of a local militia, alienation of victims, an escalating cycle of violence, rites of passage, ethnic hatred, repression of affects and collective psychological disorder. Each of these seems to have interacted with the others to bring about a brush-fire effect which resulted, within 2 weeks, in massacres, rapes and other acts of extreme violence in huge numbers in townships across the country. The danger of further violence remains high. If further repetition of the horrors of genocide is to be prevented a proper study should be made of the circumstances and the international actions that need to be taken. In addition to the Trauma Recovery Programme that is currently in train the following interventions should be considered if the cycle of violence is to be broken: economic aid to set up the industrial base that is needed to ease population pressure and allow displaced persons to return; the establishment of a system of justice that ensures that those who organized and incited the genocide will not go unpunished; a programme of re-education to counteract the effects of the programme of indoctrination that has taken place; expansion of the existing psychological support to make it available and acceptable to all of those Rwandans who have been and are continuing to be traumatized by violence and displacement.