Immunoscintigraphy is steadily asserting itself as a valuable method in the localization of malignant tumours, alongside other imaging techniques. A monoclonal antibody specific to one or several tumour cell lines is used. The antibody is labelled with a gamma emitter radioisotope and so that it can be detected in vivo. We have evaluated three monoclonal antibodies (F(ab')2 fragments): a mixture of anti-CEA and anti-19.9 antibodies in the investigation of colorectal carcinoma and the antibody OC-125 in ovarian cancer. In our experience, it appears that pelvic recurrence is the best indication for immunoscintigraphy. Antibodies can apparently be safely used in man. We noted no side-effect following the injection of anti-CEA, anti 19.9 and OC-125.