We describe four women who presented with systemic sclerosis several years after cosmetic augmentation mammoplasty with silicone-gel implants. The interval between implantation mammoplasty and the onset of systemic sclerosis ranged from 6 to 15 years. All patients fulfilled the criteria established by the American Rheumatism Association for systemic sclerosis and had Raynaud phenomenon, arthralgia, and evidence of pulmonary or gastrointestinal involvement. Enlargement of lymph nodes draining the prostheses was noted in two patients. Antinuclear antibodies were detected in three patients and showed speckled or nucleolar patterns. Removal of the prostheses in two cases did not result in improvement of systemic sclerosis. Evidence of silicone leakage from the implants included the following. The observation by light microscopy of refractile particles in tissues distant from the prostheses, the observation by electron microscopy of electron-dense structures consistent with silica, and the definitive identification of the element silicon by energy-dispersive analysis in these electron-dense structures. A marked, chronic inflammatory infiltrate containing lymphocytes, "foamy" histiocytes, and larger numbers of multi-nucleated giant cells with vacuoles and asteroid bodies was found at the same sites. Our demonstration that silicone escapes from elastomer-silicone-gel breast implants and appears to be closely associated with a chronic inflammatory reaction suggests that silicone plays a role in the development of certain cases of systemic sclerosis.