A metallic form of depleted uranium (DU) was used in weapons during the 1991 Gulf War and more recently in Bosnia and Kosovo [1]. This slightly radioactive metal is particularly toxic when it penetrates the body through inhalation, ingestion, or injury. When a depleted uranium penetrating round hits a tank, for example, substantial quantities of uranium-bearing particles may be produced and therefore inhaled by soldiers near or inside the tank. Bursts of fragments may also cause injuries. Several reports have addressed the risks to health of accidents of this nature [2]. The conclusions are normally that there is very little risk of developing cancer from internal radiological exposure to depleted uranium. Numerous uncertainties do, however, exist, particularly on the estimation of the amounts of depleted uranium likely to be inhaled. In addition, little is known on the properties of depleted uranium 22aerosols generated when firing on armored vehicles. A nonexhaustive, state-of-the-art study carried out on depleted uranium in weapons, presented later on in this chapter, is followed by a summary of experiments performed within the Institute for Radiological Protection and Nuclear Safety (IRSN) in France.