Fruiting bodies of several Suillus species contain a colourless compound, suillin, which is concentrated in the cuticle of the pileus. Its structure has been established as 4-acetoxy-3-geranyl-geranyl-1,2 -dihydroxybenzene (1) by spectroscopic evidence, conversion into a cyclic carbonate 2 and synthesis of its deacetyl derivative 3.