Hematogenous spread of tumor cells is an early event in osteosarcoma and present in the majority of patients at primary diagnosis. Eradication of such micrometastases by adjuvant combination chemotherapy is crucial for survival. However, a survival plateau of 60-70% was reached over two decades ago, above which it seems difficult to further advance with the currently available therapies. In this study we have, by an immunomagnetic isolation procedure, examined the presence and prognostic impact of disseminated tumor cells in bone marrow aspirates taken at primary diagnosis in a cohort of 41 non-metastatic patients with extremity localized, high-grade osteosarcoma.