In a prospective study, consecutive patients were treated for soft-tissue sarcoma (STS) by wide resection and adjuvant irradiation. Twelve patients had resection of bone to achieve a tumor free margin; five of these patients were left with lower extremity open segmental cortical defects in the high-dose radiation field. Four of the five patients with cortical defects suffered a fracture through the defect more than six months after surgery. Only one of 71 patients not treated with bony resection suffered a late fracture. Patients requiring bony cortex resection for STS of the lower extremity should be considered at risk for late fracture if adjuvant irradiation is prescribed.