A novel disaccharide named wilforibiose (1) was isolated from the acidic hydrolysate of the crude glycoside of Cynanchum wilfordi HEMSLEY. The structure of 1 was deduced on the basis of chemical and spectral evidence, and was confirmed to be β-D-glucopyranose L-olivopyranose 1', 4 : 2', 3-dianhydride by X-ray analysis.