Inclusion Criteria:  For study OSE A and B  Patients treated for a bone sarcoma: Ewing or osteosarcoma Age under 19 years at initial diagnosis Treated in the Pediatric Oncology Department of Gustave  For patients diagnosed between 01.01.2001 and 31.12.2010: patients alive in complete remission at least 5 years after diagnosis  Treated with at least one course of HDMTX for osteosarcoma Treated without HDMTX for Ewing sarcoma Time interval between the end of treatment and inclusion >10 y Age > 21 y at inclusion Patients with informed consent signed Patient under guardianship Affiliated to French health insurance or beneficiary of the same or equivalent  For study OSE- B only:  Treated with at least 8 courses of HDMTX for osteosarcoma Treated without HDMTX for Ewing sarcoma Patients with Ewing sarcoma will have to be matched with osteosarcoma patients according to age at the time of treatment, sex, and duration of follow-up School level equivalent of at least the end of primary school  Exclusion Criteria:  For study OSE A and B  Brain radiotherapy Previous relapse except those treated by local treatment without any chemotherapy Second malignancy treated with chemotherapy High dose chemotherapy with stem cell support Non-French speaking patients Pregnant and breastfeeding women  For study OSE- B only:  - Patient deprived of his liberty by a judicial or administrative decision