Gastrointestinal metastases of osteosarcoma are an extraordinarily rare event and, as far as we can determine, have been reported previously only 5 times; these cases represent an unusual pattern of progression. We describe a 21-year-old man with an osteosarcoma of the right tibia that was removed 4 years previously. Two years later, the patient showed lung metastases. At his most recent presentation, he complained of abdominal pain, nausea, vomiting, and anorexia. Radiologic examination revealed an abdominal mass close to the jejunum and 3 nodules in the liver. One metastasis was an ulcerated and pedunculated polypoid mass located in the mucosa of the bowel, and the other involved the entire thickness of the jejunum. This unusual phenomenon represents an alteration in the natural history of osteosarcoma as a result of increased long-term survival.