Fifty-one human palatine tonsils of both sexes and 4-54 years of age were studied for quantitative analysis of Langerhans cells in the epithelium using CD1a (T6), which is a specific immunological marker for Langerhans cells and indeterminate cells. Cryo-sections were stained using the avidin biotin peroxidase method. Using light microscopy, CD1a-positive dark brown cells with dendritic processes were identified as Langerhans cells, which were located in the epithelium, subepithelial tissue, follicles and interfollicular areas. The Langerhans cells were counted only in the tonsil epithelium per zone of 1.1 mm length of basement membrane. For each biopsy, 25 such zones were studied. The mean number (SEM) of Langerhans cells per zone of tonsil epithelium was found to be 37 (+/- 0.5). In the male, it was 36 (+/- 0.7) but in the female, it was 38 (+/- 0.2). In different age subgroups, the mean number (SEM) varied between 40 (+/- 1.7) and 14 (+/- 1.1). In the age subgroups of 11-15, 16-20, and 21-25 years, the mean number showed significant sex differences. Since the 11-15, 16-20, and 21-25 age subgroups in the female showed an increased number of Langerhans cells, it is concluded that the immunological role of the palatine tonsils is increased during puberty and adolescence. In the female, there was a negative correlation (r = -0.196, p < 0.01) between age subgroups and mean numbers, but in the male there was no correlation (r = 0.008). Overall, in all the 51 biopsies together, there was a negative correlation (r = -0.017, p < 0.01) and significant (p < 0.001) sex and age differences.