lipid infiltration as a possible biologic cause of silicone gel breast implant aging the cause of silicone gel implant aging and rupture is not known recent reports indicate the failure rate is higher than previously published and implant aging and rupture may be due to progressive mechanical deterioration of the outer vulcanized silicone shell it is known that lipids are absorbed by the hydrophobic silicone elastomer and lipid infiltration causes mechanical attenuation and possible failure of the elastomer the purposes of this article are to analyze the silicone envelopegel of explanted prostheses and the silicone elastomer of other medical grade silicone devices for lipid content and to suggest its possible role in implant aging and rupture we assayed 33 ruptured silicone breast implant shells mean age 131 years range 8 to 26 years and 8 medical grade silicone elastomer devices mean age 37 years range 3 months to 12 years for evidence of lipid infiltration using thin layer chromatography these were compared with control group assays from two nonimplanted silicone gel implants and one unused silastic catheter ninetyeight percent of implants and other previously implanted silicone devices were found to have evidence of lipid infiltration compared with none in nonimplanted controls p 0005 we conclude that lipids infiltrate the outer silicone shell and may be a factor related to breast implant aging and rupture due to progressive mechanical weakening of the outer silicone shell