The cyclotron-produced radiohalogen, 211At, is eminently suitable as a possible therapeutic radionuclide. It decays by the emission of 6.8 MeV mean energy alpha-particles, which from a radiobiological viewpoint are of near optimal therapeutic LET. This paper reviews developments in the possible application of [211At]astato-labelled molecules as potential anti-tumour agents. Additionally, radio-dosimetric evidence is presented, and its implications for human cancer therapy are discussed.