A morphometric analysis was performed of the Langerhans' cell density in epithelial sheets obtained from normal exocervices and from exocervices with squamous carcinoma. Laminae of exocervices with squamous carcinoma that showed cervical intraepithelial neoplasia (CIN) were classified according to its predominant degree of severity as CIN I, CIN II and CIN III or as normal when no neoplastic changes were found. Laminae with CIN showed a higher Langerhans' cell density than the laminae from normal exocervices and than the normal laminae of exocervices with carcinoma. The magnitude of the increase of Langerhans' cell density and the degree of severity of the neoplastic changes appear as closely related phenomena. An increase of the more ramified types of Langerhans' cell in the laminae containing CIN was found, with the most ramified being more frequent in the most severe lesions.