Eleven patients, aged 36 to 55 years, with silicone breast implants had episodes of severe chest pain similar to heart attacks 6 weeks to 7 years after breast implantation; one patient had a severe attack 1 month after explantation. The chest pain, which was not related to physical exertion, lasted from 15 minutes to 4 days, and descriptions of it varied from a "pressing" type of pain to "stabbing" pain with radiation to the shoulders, left arm, and jaw. The associated symptoms were diaphoresis, nausea, vomiting, dyspnea, and palpitations. All of the patients had a normal electrocardiogram (ECG) with the exception of one, whose ECG showed nonspecific ST changes. Ten had cardiac evaluations, all of which yielded normal results. All had implant removal, and five were found to have at least one ruptured implant. Nine had an implant capsule biopsy; all had chronic inflammatory rinds, and five had free silicone in tissue whether or not the implants were ruptured. All eight who had a pectoralis major muscle biopsy had abnormal results: (neurogenic atrophy [six], fasciitis [three], myositis [one], chronic inflammation [one], free silicone [one], and neuroma [one]). We concluded that silicone breast implants may cause an atypical chest pain syndrome, probably due to local inflammatory reactions and neuroma formation.