Limb-saving procedures for patients with osteosarcomas of the extremities are based on the anatomical localization and extent of the tumor. The effectiveness of neoadjuvant chemotherapy, high-dose methotrexate (HD MTX), was prospectively analyzed in patients using magnetic resonance imaging (MRI) and histologic evaluation of bone biopsies. Evaluation of in vivo response to neoadjuvant chemotherapy for osteosarcomas with MRI is a method which seems promising in predicting the histologic tumor reaction.