The distribution of basement membrane laminin was investigated in normal endometrium and cervix, as well as in a variety of non-neoplastic and neoplastic lesions of these tissues. Normal epithelial structures were surrounded by a generally intact basement membrane. Minor breaks in continuity and alterations of linearity were seen in association with inflammation and stromal fibrosis. Metaplasias, atypical hyperplasias, dysplasias, and in situ carcinomas characteristically rested on an essentially intact basement membrane, although minor disruptions were seen, occasionally in association with inflammation. Superficially and deeply invasive adenocarcinomas and squamous carcinomas exhibited impaired laminin production. In well differentiated carcinomas of the endometrium and cervix, an intact basement membrane was often seen around infiltrating glandular and squamous elements, although focal reduplications and small disruptions were seen in all cases. In high-grade carcinomas, considerable impairment of basement membrane integrity was seen, but immunostainable laminin was still evident, at least focally, in all cases. The findings confirm that endometrial and cervical carcinomas, even those of high histologic grade, are capable of basement membrane production.