Malignant tumours of the locomotor apparatus in children mainly comprise bone tumours such as osteosarcoma or Ewing's sarcoma and soft tissue sarcomas such as rhabdomyosarcoma. The diagnosis must be considered in any case of progressively worsening limb pain at a fixed site, possibly associated with a soft tissue mass. Standard radiological examinations, Doppler ultrasound, then MRI confirm the diagnosis of a solid tumour, allow staging and may sometimes suggest the invasive nature of the tumour. The biopsy provides a precise histological diagnosis. A frozen section is usually necessary to confirm this diagnosis using the currently available genetic biology tools. Treatment must be adapted to the known prognostic factors, mainly tumour operability, initial size, histological type, response to neoadjuvant chemotherapy and initial staging. Treatment must comprise neoadjuvant chemotherapy followed by local treatment combining radical surgery with reconstruction if necessary and sometimes external beam radiotherapy. This treatment must be completed by postoperative adjuvant chemotherapy resulting in an average total duration of treatment between 6 and 12 months. Long-term follow-up is designed to ensure absence of disease recurrence, attentive orthopaedic follow-up and absence of late sequelae related to anticancer therapy.