After 30 years of development, therapy with monoclonal antibodies has started to realize its promise. Clinical use is most widespread in the field of oncology, where half of the agents approved for routine clinical use are employed and a large number of molecules are currently undergoing clinical trials. In the past 2 years alone, three new compounds-the radiolabeled antibody (131)I-tositumomab and two antibodies targeting growth factor receptors (bevacizumab and cetuximab)-have received FDA approval for indications in oncology. This review summarizes the development of this exciting treatment modality over the last three decades, examines the outcome of treatment with these new antibodies and others available for routine clinical use (i.e. rituximab, trastuzumab, alemtuzumab, gemtuzumab ozogamicin, (90)Y-ibritumomab tiuxetan) in standard indications and in experimental settings, and gives a brief outlook on possible future developments.