Silicone prosthesis-based breast augmentation has shown year-on-year increases in popularity in both the USA and UK, but as surgical and implant technologies improve, adverse capsular contracture (ACC) has become a key determinant of outcome. ACC is the term given to the abnormal soft tissue reaction to a foreign body leading to constrictive fibrosis. Constrictive fibrosis refers to the poorly understood phenomenon by which the capsule that normally envelops an implant shrinks in size. The formation of a capsule around any foreign material entering the body is a normal response of the organism, which is not normally pathological in nature. This book discusses this adverse capsule and its role in breast augmentation.