A method is described to isolate and characterize human skin dendritic cells (DC). This method is based on the migratory capacities of these cells. The cells migrated 'spontaneously' out of split-skin explants into the medium during a 24-h culture period and contained up to 75% CD1a+ cells. After removal of co-migrated T cells and macrophages, the highly enriched (> 95% CD1a+) DC showed potent allo-antigen-presenting capacities. About 25% of the CD1a+ cells were also positive for the dermal DC marker CD1b, whereas only 15-20% of the cells contained Birbeck granules, the characteristic cell organelle of the epidermal Langerhans cell. Before culture, CD1a+ DC were observed on cryostat sections not only in the epidermis but also in the dermis. After culture, the number of CD1a+ cells in both epidermis and dermis had decreased. Not all the cells had migrated during the culture period; some CD1a+ cells could still be detected in the epidermis and dermis after culture. Thus, using this method, potent allo-stimulating CD1a+ cells, migrating from both epidermis and dermis, can be obtained without the use of enzymes.