In studying the mechanisms that regulate the growth and differentiation of the human epidermis, it would be helpful to obtain relatively pure populations of the different epidermal cell types. We have used a solid-phase immunoabsorption method termed "panning" to positively select two types of epidermal cells: Langerhans cells and the keratinocytes found in the basal cell layer (basal cells). To attach basal cells to a goat anti-mouse IgG-coated plastic surface, we used murine monoclonal antibodies (VM-1 or VM-2), which were recently produced in our laboratory and bind specifically to antigens on human basal cells. Using antibodies VM-1 or VM-2, we panned for basal cells and obtained a yield of about 40 percent (an enrichment of about 2.5-fold). The cells enriched for basal cells demonstrated much better growth and DNA synthesis than did the cell fraction depleted of basal cells. For positive selection of Langerhans cells, we used OKT6, a murine monoclonal antibody that binds specifically to Langerhans cells in the epidermis. We determined that of those cells preincubated with OKT6 and adherent to an antibody-coated petri dish surface, about 70 percent demonstrated OKT6 binding by fluorescence microscopy. This represents a 15- to 20-fold enrichment for Langerhans cells. The nonadherent cell fraction contained less than 1 percent OKT6-positive cells. Ultrastructural studies showed that the cells thus separated were Langerhans cells. The OKT6-positive but not the OKT6-negative cells were capable of stimulating allogeneic lymphocytes in the skin-cell-lymphocyte reaction. Thus the panning technique is an effective method for obtaining greatly enriched subpopulations of viable epidermal cells.