Background and Objectives: Assessment of chemosensitivity in patients with osteosarcoma may help identify those with resistance to chemotherapy. In this study, we investigated the clinical value of the doxorubicin binding assay in its ability to identify patients with drug resistance. Methods: We tested tumor tissue samples obtained at biopsy of 24 patients with high-grade osteosarcoma aged 9-61 years (mean 19.2) for sensitivity to doxorubicin, using the doxorubicin binding assay. Tumor excision was performed in these patients after neoadjuvant chemotherapy. Chemotherapy response was judged on the basis of tumor necrosis achieved and was compared with doxorubicin sensitivity in each of these patients. Results: Doxorubicin sensitivity was good in 15 and poor in 9 of 24 patients studied. In patients with good sensitivity (n β«Χ‘β¬ 15), 9 (60%) exhibited a good response to chemotherapy while response was poor in 6. In patients with poor sensitivity (n β«Χ‘β¬ 9), response to chemotherapy was poor in all 9 (100%) patients and 7 (77.8%) of these patients developed metastatic disease within a mean period of 5.2 months, resulting in two deaths. The results were statistically significant at P β«Χ‘β¬ 0.0193. Conclusions: Doxorubicin binding assay may be useful in identifying patients with inherent resistance to chemotherapy. As the outcome of patients showing resistance to doxorubicin is poor, innovative strategies may need to be developed for this group of patients.