Several different injectable substances have been employed to increase breast volume, including paraffin, petroleum derivatives, vegetable oils, and silicone. Of these, liquid silicone injection has been used most frequently, especially throughout the 1950s and 1960s, because it was considered an “inert” material, meaning that it should result in fewer complications. This chapter details the various ways by which free silicone is recognized and differentiated from other injected substances—in mammography, ultrasound, and magnetic resonance images; how its presence interferes with these commonly-used diagnostic tools’ ability to recognize breast pathology; and the knowledge necessary in clinical practice to reach accurate diagnoses when silicone is present. It should be noted that the most common objective of the above-listed breast-imaging methods is to diagnose breast cancer early and that interfering with this risks patients’ quality of life and survival. Although mammography and ultrasound are readily accessible diagnostic tools that allow clinicians to diagnose siliconomas with virtual certainty, contrast-enhanced magnetic resonance imaging (MRI) is the method of choice to study silicone-related complications. It also is the diagnostic tool that must be used for breast cancer detection.