The development of heterotopic ossification (HO) as a complication of toxic epidermal necrolysis (TEN) has not been previously reported. TEN, also known as Lyell's syndrome, is a rare but serious skin disorder that typically occurs after the administration of drugs, especially sulfonamides, barbiturates, phenytoin, and nonsteroidal anti-inflammatory agents. TEN is characterized by the development of large fluid-filled bullae with separation of large sheets of skin. Complications of TEN can include extensive denudation of skin with dehydration and electrolyte abnormalities, gastrointestinal hemorrhage, acute tubular necrosis, secondary infection of denuded skin, pneumonia, bacterial conjunctivitis, keratitis, and septic infarcts of internal organs. We report a case of HO in a patient with TEN after treatment with trimethoprim-sulfamethoxazole. A 49-year-old man developed an erythematous rash, bullae, fever, and extensive skin loss consistent with a diagnosis of TEN. He was intubated for complications of TEN (pneumonia) and maintained on bed rest for several weeks. In addition, he developed HO that resulted in multiple joint contractures. He was treated with aggressive range of motion by physical therapy, surgical resection of the HO followed by radiation to both elbows, right hip, and right knee. Postoperative outpatient rehabilitation enabled improved function in his mobility and activities of daily living. HO is known to occur after spinal cord and brain injuries and burns. It has not been reported to occur after TEN. Our experience with this case suggests that HO may merit inclusion into the list of complications of TEN.