Glycyl-d-threonine dihydrate, C6H12N2O4· 2H2O, is orthorhombic, with space groupP212121,a= 9.6211(3),b= 10.0313(2),c= 10.6642(4) Å,Z= 4. Crystals were grown from a solution of the racemic mixture glycyl-d,l-threonine. The structure was refined toR= 0.025 for 2140 reflections of the typehkland¯hkl; the absolute configuration of the sample crystal was determined from the anomalous scattering of CuKα radiation by C, N, and O. The N-H and O-H bond distances and, especially, bond angles seem to be strongly influenced by the positions of the hydrogen-bond accept