The crystal structure of (+_)-Cr(en)s(SCN) 3 . 0.75 HzO has been determined by single-crystal X-ray diffraction analysis. It is monoclinic with space group P2~/b. The lattice constants are: a = 15.740 _+ 0.008, b = 17.77 _+ 0.01, c = 9.460 + 0.007/~, y = 131.08 + 0.08 °, with four formula units in the unit cell. The structure was refined by full-matrix least square methods with anisotropic thermal parameters to a final R of 0.069 for 4892 reflexions. One of the three chelated rings (en) of ICr(en) 313+ has a disorder of conformation which has been studied: the configuration of (+)-[Cr(en)3] 3+ is A [66(70% 6, 30% A)I; complex ions, SCN and H20 are linked by hydrogen bonds N-H... N, N-H... S, and O-H-..S. Two of the three independent SCN groups have three hydrogen bonds to their S atoms and two to their N atoms: they bridge three complex ions [Cr(en)3] 3+. The third SCN is attached to one complex by its N atom, and to one water molecule by its S atom. There is a correlation between disorder in the conformation and hydrogen-bond interactions.