The local inflammatory cell infiltrates in 263 cervical punch biopsies of the women followed-up since 1981 (16 +/- 14 months, mean +/- S.D.) for an established human papillomavirus (HPV) lesion with or without concomitant cervical intraepithelial neoplasia (CIN) were analysed for occurrence of Langerhans cells, defined by the monoclonal antibody OKT-6 using the avidin-biotin peroxidase complex (ABC) technique. OKT-6+ cells remained at the constant low level (1.5-1.9% of the inflammatory cells) in the different types of HPV lesions (flat, inverted or papillomatous condylomas), their percentages (range 0.8-2.1% of the cells) being slightly affected by the grade of HPV-associated CIN, however, (P less than 0.05 between HPV-CIN I and HPV-CIS). Although cervical HPV lesions characteristically are a disease of young females, the relative levels of in situ Langerhans cells did not show any age-dependence. Furthermore, the intensity of the inflammatory cell infiltrate did not correlate with the relative levels of OKT-6+ cells in the biopsies. Practically identical (1.6%) levels of OKT-6+ cells were found in the first biopsies of the HPV lesions shown to regress during the follow-up period (28.8% of cases), when compared with those (1.7%) in the lesions persisted (52.1% of cases) or progressed (19.1% of lesions). The results are discussed in terms of the proposed immune surveillance function against viral infections, attributed to Langerhans cells in the SALT/MALT concept.(ABSTRACT TRUNCATED AT 250 WORDS)