This article explores the question of whether the war on terror is just. It begins by arguing that the Just War tradition offers a better way of asking moral questions about war than either pacifism or realism. Applying the Just War tradition suggests that in order to justify a war on terrorism, we need to know exactly who the terrorists are and whether they have given us just cause for war. The war on terror as conceived by the Bush administration does not satisfy these tests because it threatens to wage war on those who have done no wrong and constitutes a disproportionate response. Whilst the war on terror may be unjust, war against specific terrorists may certainly be justifiable. The final part of the article explores some of the jus in bello elements of the war on terror and raises grave concerns about the way that the US and its allies are conducting the war.