In the present study we have evaluated whether monoclonal antibodies (MAbs) B72.3 and AR-3 which display, on histological preparations, a differential reactivity with normal and transformed endometrium, could be a useful adjunct to endometrial cytology in the identification of pre-neoplastic and neoplastic conditions. Immunocytochemical (ICC) tests, using the 2 reagents, were performed on normal cycling endometrium and on hyperplastic and malignant lesions collected by the endocyte technique both from 86 surgically resected specimens and from 62 postmenopausal symptomatic and asymptomatic outpatients. The results obtained showed that the combination of the 2 MAbs can complement conventional morphology in the identification of pre-malignant atypical lesions and endometrial carcinoma of unclear cytological features, thus allowing a selection of those patients who are candidates for fractional curettage.