Saline-filled prostheses are currently the only type of prostheses available for cosmetic use in the United States because of concerns raised about the possibility of systemic toxicity of silicone-filled artificial mammary implants. Although the approved implants are saline-filled, their potential to release silicone particles from the shells has not been systematically evaluated. We performed microscopic examination of the pericapsular tissue of 54 patients with textured-surface implants and compared these with 51 patients with smooth-walled implants over a 2-year period. The capsules that had formed around virtually all textured-surface implants had silicone fragments present either in extracellular spaces, in vacuolated histiocytes, or in the form of foreign-body granulomas in surrounding fibroadipose tissue but not in capsules associated with smooth-walled implants. In 87 percent of samples of pericapsular tissue from textured saline implants, the contact surface displayed exuberant reactive synovial metaplasia, a histologic pattern not previously described with these devices. Our findings suggest that smooth-walled prostheses are associated with less silicone fragmentation than textured devices in the peri-implant tissue capsules that tend to form around artificial surfaces used for this purpose.