With the advances in genomics, molecular biology including gene vector technologies today's molecular imaging modalities have strongly been improved. The major progress is based on peptide and antibody targeting vectors. When labeled with beta(-)-emitting radioisotopes these agents are applicable for endoradiotherapy and exploit the targeting potential for highly specific therapeutic applications. This novel class of pharmaceuticals offers the potential to develop patient specific therapies and might provide the means to go beyond the possibilities of current chemotherapy and radiation therapy. In this review the basic principles of endoradiotherapeutics based on peptides and proteins are presented. Several of these drugs such as (90)Y-rituximab (Zevalin), (131)I-tositumomab (Bexxar) and the somatostatin receptor binding (90)Y-DOTATOC that are nowadays successfully applied in oncological therapy are discussed. Future generations of endoradiopharmaceuticals will address yet unknown targets which might be identified by screening techniques such as ribosome and phage display peptide libraries.