Depleted uranium is a by-product of the process of enrichment of natural uranium and is classified as a toxic and radioactive waste; it has a very high density (approximately 19 g cm-3), a remarkable ductility and a cost low enough to be attractive for some particular technical applications. Civilian uses are essentially related to its high density, but the prevailing use is however military (production of projectiles). From the radioactive point of view, the exposure to depleted uranium can result from both external irradiation as well as internal contamination. The associated risks are however mainly of chemical-toxicological kind and the target organ is the kidney. In the present note the recent military uses and the possible effects of its environmental diffusion are discussed.