Abstract CD1a is often used as marker for dendritic cells (DCs) in vitro and in vivo . The density of CD1a + DCs within human tumours has been associated with survival. The functions of CD1a and the other members of the CD1 family have long been unclear but in recent years it has emerged that CD1 molecules present non-peptide antigens to T cells. Many of the antigens presented by CD1 molecules have been identified as glycolipids. Because many tumour-specific glycolipids are known to be immunogenic, we hypothesize that these tumour-specific glycolipids can also be presented by CD1a to T cells, and induce CD1a-restricted tumour-specific T-cell responses. Modulation of CD1a expression on tumour-infiltrating DCs is discussed in this context.