Radioisotope therapy is an internal form of radiation used to treat cancer; it may be administered orally or intravenously and represents the nearest treatment option to the 'magic bullet', specifically targeting sites of disease whilst sparing surrounding normal tissues. Radioisotope therapy has an important role to play in modern medicine, particularly in the treatment of thyroid disease, neuroendocrine tumours, bone metastasis and non-Hodgkin's lymphoma. It is found in both thediagnostic setting and in therapy, but recently there has been a renaissance in the application of radioisotope uns