There are many radiological interventions necessary for pediatric oncology patients. some of which may be covered in other articles in this publication. I will discuss a number of interventions including percutaneous biopsy for solid tumor and hematological malignancy diagnosis or recurrence, for the diagnosis of graft versus host disease after stem cell or bone marrow transplantation. and for the diagnosis of complications of immunosuppression such as invasive pulmonary aspergillosis. In the past, tumor localization techniques have been necessary to biopsy or resect small lesions. However improved guidance techniques, have allowed for more precise biopsy and the use of thermal ablation instead of excision for local tumor control. A percutaneously placed radio frequency, microwave, laser or cryogen probe can ablate the primary and metastatic rumors, of the liver. lung. bone, kidney and other structures in children. This is an alternative treatment for the local control of tumors that may not be amenable to surgery. chemotherapy or radiotherapy. I will also describe how chemoembolization can be used to treat primary, or metastatic tumors of the liver that have failed other therapies. This treatment delivers chemotherapy in the hepatic artery infused with emboli to increase the dwell time and concentration of the agents. (C) 2004 Elsevier Ireland Ltd. All rights reserved.