Summary. Cryostat sections of healthy cervical, vaginal and vulva1 epithelium were examined using immunohistological labelling techniques and a panel of monoclonal antibodies recognizing Langerhans' cells, T- and B-lymphocytes and HLA-DR antigen. The distribution of Langerhans' cells in squamous epithelium of the cervix, vagina and vulva showed a marked variation with the highest median values in the vulva (18·7 per 100 basal squamous cells) and the lowest in the vagina (5·5 per 100 basal squamous cells). There was also a substantial variation in number and distribution of lymphocytes of each of these three areas with a distinct preponderance in the transformation zone of the cervix. In addition, intraepithelial lymphocytes, predominantly of the T-cytotoxic suppressor sub-type were present at all sites with the greatest number in the transformation zone. We conclude from this study that lymphoid tissue of the cervical transformation zone has several unique characteristics which are not observed at other sites in the lower genital tract. We suggest that this tissue be designated ‘cervical lymphoid tissue’ and that it forms a part of the ‘mucosal associated lymphoid tissue’ (MALT) as noted at other mucosal sites exposed to the external environment.