The percent of modern silicone gel breast implants that fail due to shell rupture is quite low, amounting to less than 1% per year. Nonetheless, extensive retrieval and analysis studies are being conducted on failed devices returned to Allergan Medical (formerly Inamed Corporation) in order to determine the modes and causes of failure. With the modes and causes known, solutions can be implemented to eliminate the failure mechanisms. Analyses conducted thus far have demonstrated that there are several causes of breast implant failure. The focus of this paper is on one type of silicone gel breast implant failure, i.e., a failure associated with a fold or wrinkle, which is termed "fold flaw failure." Although fold flaw failure is not a dominant mode of failure for silicone gel breast implants, its failure characteristics must be understood in order for this type of shell rupture to be detected and eventually eliminated. In this study, optical microscopy and scanning electron microscopy are used to describe the morphology of fold flaw failure for explanted silicone gel breast implants with smooth shells. The microscopy analysis demonstrates that there are several different types of shell failure patterns that can be produced by a fold or wrinkle in a silicone gel breast implant.