Fibrodysplasia ossificans progressiva (FOP) is a rare heritable disorder characterized by progressive heterotopic endochondral bone formation arising in ligament, tendon, and the fibrous connective tissue of skeletal muscle. The disorder is almost invariably associated with skeletal malformations of the endochondral anlage of the feet. A 25-year-old woman with FOP had a histopathologically documented phalangeal enchondroma. This common neoplasm of cartilage and bone seems not to have been previously reported in FOP; it may represent a coincidental occurrence, but in the context of the patient's genetic disorder, an enchondroma may represent an unusual and variable expression of the disease.