Radioimmunoguided surgery is useful in detection of both primary and secondary malignancies. The specificity of the monoclonal antibody B 72.3 allows direct targeting of tumor cells. The Neoprobe (TM) hand-held gamma detector can then localize the tumor and delineate tumor margins. More importantly, it can identify disease that is not detectable by routine imaging or by a surgeon's intraoperative inspection and palpation.