The use of radiolabeled monoclonal antibodies as a diagnostic tool in nuclear medicine has grown rapidly over the past several years. Early studies utilized antibodies labeled with radionuclides of iodine (i.e. 125I and 131I) although these radionuclides are not ideal for use in tumor imaging. Recent advances and the development of new chemical methods has made it possible to label antibodies with other radionuclides (i.e. 77Br, 111In and 99mTc). The advantages and disadvantages associated with all of the different radionuclides and labeling methods will be discussed.