Although radionuclide therapy has been around for a long time, this modality of cancer treatment has been limited mainly to the use of [32P]-phosphate and [131I]-sodium iodide. The last few years, however, have seen an increased interest in this area due to new developments of radionuclides and carrier molecules that may provide selective targeting of tumour sites. The potential of this technique can be further realized if the radionuclide is carefully selected to match both the localization of the carrier molecule and tumour morphology. This paper briefly reviews radionuclides in current use and potential candidates for targeted therapy. Decay characteristics, production methods and relevant chemical properties are discussed.