The title compound, C(12)H(22)O(11)·2H(2)O {systematic name: 6,6'-oxybis[2-(hy-droxy-meth-yl)-3,4,5,6-tetra-hydro-2H-pyran-3,4,5-triol] dihydrate}, is a disaccharide, which was isolated from Tremella fuciformis. The mol-ecule contains two six-membered rings, both of which adopt a chair conformation. Extensive O-H⋯O hydrogen bonds occur in the crystal structure.