Alpha-galactosylceramides are potent stimulators of human T cells. Stimulation occurs through binding of the glycolipids by CD1d, presentation to T cells, and formation of a CD1d-glycolipid-T cell receptor complex. To facilitate the elucidation of the structural features of glycolipids necessary for T cell stimulation, alpha-galactosylceramides have been prepared with small molecules appended at the C6 position of the sugar. The appended molecules do not significantly influence the abilities of the glycolipids to stimulate T cells. [reaction: see text]