The specimens were obtained from 7 fibrous capsules two years after mammoplasty with silicone prosthesis, and were examined by electron spin resonance (ESR) andmicroscope. The result showed that a marked quantities of oxygen free radical existed in the capsules and that the main pathological change was the infiltration of massive inflammatory cells and deposition of collagen. It was suggested that the fibrous capsule formation was concerned with the oxygen free radical. The origin of the oxygen free radical in mammoplasty with slicone was also discussed.
