Langerhans cells were detected in squamous, stratified epithelia lining human dermoid cysts. Their presence was assayed by ATPase staining and reactivity with heteroantisera against “Ia‐like” antigens. Transmission electron microscopic; studies demonstrated variations in the numbers of cells showing Birbeck granules in epithelia with different degrees of keratinzation. Indeterminate cells (i.e. lacking granules), were more frequent in epithelia showing combined mucous and keratinizing differentiation. Membrane‐coating‐granules and keratohyalin granules were present in epithelia containing Langerhans cells with clearly identifiable Birbeck granules. Interepithelial mast cells were observed in epithelia with mucous differentiation. A relationship between Langerhans cells and kerutinization was suggested. Such non‐immune functions are compatible with the known macrophage characteristics