In this work, we studied the localization and traffic of CD1a molecules in human epidermal Langerhans cells and the ability of these cells to stimulate CD1a-restricted T cell clones. We found that CD1a was spontaneously internalized into freshly isolated Langerhans cells, where it was rapidly distributed to the early/sorting endosomes and then to the early/recycling endosomes. In the latter compartments, CD1a colocalized with Rab11, a small GTPase known to be involved in the recycling of transmembrane proteins from early endosomes to the cell surface. In the steady state, intracellular CD1a was mainly located in Rab11+ recycling endosomal compartments. When endocytosis was blocked, intracellular CD1a moved rapidly from the early/recycling endosomes to the cell surface where it accumulated. The resultant increase in the cell surface expression of CD1a enhanced the capacity of Langerhans cells to stimulate a CD1a-restricted T cell clone. These findings are consistent with a dynamic exchange of CD1a between recycling compartments and the plasma membrane and suggest that the antigen-presenting function of CD1a depends on its traffic through the early/recycling endosomal pathway.