There has been little improvement in outcome for patients with osteosarcoma (OS) over the last 20 years. There have been only a few clinical trials of new treatments and no major new therapies introduced recently. This is in part because there is no good understanding of the biology of osteosarcoma, but also trials have only included subgroups of patients. The more that is understood about how and why osteosarcoma arises and grows the better clinicians will be able to decide what treatments are most likely to work best. The purpose of this project is to collect high quality clinical data about patients of all ages with osteosarcoma, such as information about the size of the disease, how it was diagnosed and where it is at diagnosis, what treatments were given and how the disease responded the treatments. Blood and tissue samples will also be collected for analysis in research laboratories. By looking at the results of the laboratory findings and the clinical data together, the questions will start to be answered about why osteosarcomas arise and grow, what makes it spread, and why some patients respond to treatment better than others. As time goes on, this information is planned to be used to develop clinical trials of new treatments. Alongside this, the aim is to find out more about how osteosarcoma and its treatments affect the lives of those living with this disease. This information will help provide the most appropriate care and support that will meet the needs of each patient. Ultimately, the aim is to improve the care and treatment of osteosarcoma patients so that they may live longer and better lives.