At present the only specific way to identify epidermal components is with the electron microscope. Using the latter it has been shown that there are three forms of dendritic cells in human epidermis. The first two, the melanocyte and Langerhans' cell, vary in number and location in different regions of the body while the indeterminate type remains rather constant and is located in the lower levels of the epidermis. Quantitative studies suggest an absence of melanocytes and an increase in volume of Langerhans' cells in absolute vitiliginous skin.