CD1 molecules present both self lipids and microbial lipids. Recent studies have elucidated novel antigenic structures that can be presented by CD1 for T cell stimulation, as well as new pathways for lipid-antigen presentation. Additionally, the development of lipid-CD1 tetramers now permits the tracking of CD1-reactive T cells during immune responses. Despite this, the roles of CD1-reactive T cells in both host defense and immune regulation remain to be unequivocally defined.