Erlose [beta-D-fructofuranosyl O-alpha-D-glucopyranosyl-(1-->4)-D-glucopyranoside] trihydrate, C18H32 O16.3H2O, M(r) = 558.48, is orthorhombic, P2(1)2(1)2(1) with a = 31.164(7), b = 13.111(5), c = 11.636(5) A, and Z = 8. The structure was solved by direct methods, and refined to R = 0.035 for 3926 observed reflections. The unit cell contains two independent molecules having a similar conformation. The conformation of the alpha-(1-->2) glycosidic linkage is similar to that observed in erlose monohydrate, whereas the conformation of the alpha-(1-->4) glycosidic linkage differs significantly. The molecule has no intramolecular hydrogen-bonds except for the minor components of three-center bonds, but indirect intramolecular hydrogen-bonds through the water molecules are formed. The hydrogen-bond system in the crystal structure consists of infinite and finite chains crosslinked by water molecules.