Radioimmunoscintigraphy (RIS) with technetium-99m labelled SM3, a monoclonal antibody reacting with a polymorphic epithelial mucin glycoprotein core antigen, is evaluated. No adverse effects or thyroid uptake were observed. Studies in 45 patients (one twice) had a sensitivity for gynaecological malignancy of 100% (35/35) and a specificity of 73% (8/11), giving an overall accuracy of 93% (43/46). These results have led to the routine adoption of 99mTc RIS in the management of patients suspected of or having primary or recurrent gynaecological cancer.