Radioimmunoscintigraphy with SM-3 monoclonal antibody produces results similar to those obtained with 123I-labeled HMFG-2. The tumor specificity of SM-3 in vitro is not as marked as that in vivo. SM-3 is, however, much easier to produce in tissue culture and, with the availability of 99mTc labelling, has allowed radioimmunoscintigraphy to be done as an outpatient procedure. This technique has important implications for the continuing management of patients with ovarian cancer.