This paper rewiews the research in the field of radiopharmacology of metal-ligand-complexes with radioactive central ion in the last ten years. The investigations, carried out mainly in close cooperation between radiochemists and nuclear medicine physicists, intended the elucidation of mechanisms which are responsible for the tumour accumulation of radioactive metals like67Ga,167Tm,169Yb or90Y, injected as metal-ligand-complexes. Improvement of tumour scintigraphy by means of such complexes was the practical background of our investigations. The ratio of tumour/background radioactivity obtained using these compounds depends on their biokinetics, the mechanisms by which they are accumulated in tumour tissue, and the transport processes in blood. To investigate these problems we studied possibilities to influence the biokinetics of radioactive metals, applied as metal-ligand-complexes in order to optimize the radioactivity concentration in tumours in comparison with those in other body tissues. At present we attempt to exploit our results for the therapeutic use of metal ligand complexes by testing therapeutic effective radionuclides as central ions in the complexes.