Antibody-guided diagnosis can provide information regarding malignant disease which is not obtainable by conventional techniques and in some instances this approach can help to achieve prolonged tumour-free survival. Nevertheless, there are many technology improvements that need to be made if this method is to be widely applied for routine diagnosis and therapy. Already, encouraging therapeutic responses have been reported using 131Ilabelled polyclonal and monoclonal antibodies in the treatment of primary and metastatic liver tumours. It is essential, however, to improve the radiolabelling of monoclonal antibodies for therapeutic use. It would be more convenient and effective to use radioactive isotopes which are pure beta emitters, e.g. 90Y and 32P which would allow for outpatient therapy. It is essential to evaluate the use of multiple antibodies or antibodies that bind to multiple antigenic targets within tumours to improve dose rate and total dose amplification. Finally, encouraging clinical pilot studies should be followed up by documented randomized clinical trials in order to define properly the clinical place of monoclonal antibodies, in both the diagnosis and the therapy of malignant disease, including primary and metastatic liver tumours.