Benign bone cysts (aneurysmal and unicameral) often require treatment to prevent pathological fractures. Percutaneous injections are less invasive than surgery. We describe the different percutaneous treatments available: local injection of steroids, calcitonin, or bone marrow in unicameral bone cysts, and Ethibloc(R)(Ethicon, Ethnor Laboratories, Nevilly Sur Seine, France) injection in both unicameral or aneurysmal bone cysts. Within the tumor, histologic modifications usually occur after these injections, due to the fibrogenic properties of the agent. Therefore, we emphasize the necessity of obtaining an histologic proof before any injection, especially in aneurysmal bone cysts.