When radio-iodine was first used in the treatment of metastasized thyroid carcinoma in 1943, its success in terms of tumour response, quality of life improvement and survival was considered a 'miracle', as in those days metastatic cancer was generally fatal. Inspired by this, many efforts have been made to apply radioisotope therapy to other tumours. Radionuclide therapy uses radioactive isotopes labelled with specific targeting agents that aim to deliver the irradiation of the isotope to the tumour, while sparing normal tissues. Its unique modality allows to systemically target radiosensitive tumours throughout the body. Another important principle is its so-called 'cross-fire' action, whereby, owing to the larger reach of the radiation in relation to the cell diameter, a tumour cell receives lethal hits also from isotopes in the neighbourhood that are not directly associated with this cell. The treatment is therefore less hampered by inhomogeneous distribution and metabolism than for example chemo- or immunotherapy. The European Association of Nuclear Medicine has issued guidelines on so-called 'established' therapies (www.eanm.org), i.e. hyperthyroidism, thyroid carcinoma, refractory synovitis, bone metastases, mIBG therapy, 32P therapy and Lipiodol therapy. Newer therapies include radio-peptide therapy, radio-immunotherapy of lymphoma and microsphere therapy for liver cancer. The aim of a recently held workshop at the ECCO13 conference 2005 and this review is to inform the oncology community about these new developing therapies.