The CTB (Chernobyl Tissue Bank) is a unique venture. It is the first international cooperation that seeks to establish a collection of biological samples from tumours and normal tissues from patients for whom the aetiology of their disease is known – exposure to radioiodine in childhood. The project, which started in October 1998, has been supported by a number of sponsors including the European Commission, the WHO, the National Cancer Institute (NCI) of the USA and the Sasakawa Memorial Health Foundation of Japan (SMHF). The project is currently jointly funded by the NCI and the SMHF. The project is coordinated from Imperial College, London and works with Institutes in the Russian Federation (the Medical Radiological Research Centre in Obninsk) and Ukraine (the Institute of Endocrinology and Metabolism in Kiev) to support local scientists and clinicians to manage and run a tissue bank for those patients who have developed thyroid tumours following exposure to radiation from the Chernobyl accident. Belarus was also initially included in the project, but is currently suspended for political reasons.