Abstract: In this communication we observed the densities and distribution of Langerhans cells, T cells and their subsets, B cells and macrophages in seborrheic keratosis, verrucous nevus, Bowen's disease, basal cell carcinoma and squamous cell carcinoma with a panel of mono-clonal antibodies employng ABC immunopero-xidase technique. It was found that the densities of Langerhans cells in the epidermis of tumors were higher than those of the normal epidermis. The Langerhans cell densities within the cancer nests were much lower than the normal control epidermis. The main infiltrating cells in various tumors were T cells with scattering macrophages. B cells were rarely seen. These results indicate that the lowered Langerhans cell density may be of relevance to the impaired local immune surveillance function and T cell mediated cellular immunity may play a vital role in the anti-tumor immune response.