Glycoglycerolipid analogues, characterized by a glycerol aglicone beta-linked in position 2 to a glucose or galactose residue, and by a lipophilic C6 acyl chain on the glycerol unit, significantly inhibit proliferation of activated T cells. The inhibitory activity displayed by such synthetic compounds is comparable to the immunosuppressive properties shown by the natural glycolipids simplexides, to which they are structurally related. Vice versa, when the acyl chain is located on the sugar unit, no immunomodulating activity is observed, suggesting a strict relationship between the activity and the location of the acyl chain.