Several armies worldwide use depleted uranium in ammunition. DU is quite cheap, available in large quantities and its high density allows the use in armor-penetrating or bunker busting weapons. Despite these advantages, the use of DU is prohibited by international humanitarian law as is shown in this article. In the first part, it will be examined by presenting recent medical research that DU might cause superfluous injuries to combatants - a clear violation of international humanitarian law. Moreover, it will be elaborated in the second part that in certain cases the use of DU has effects which cannot be limited to combatants, but which also affect non-combatants - which constitutes another violation of international humanitarian law. Furthermore, DU has an impact on the environment, although this impact does not meet the high threshold needed to assert another violation of international humanitarian law - at least according to up to date research.