Crystals of uridine, C9HI2N206, are monoclinic, space group P21 with a=4.981 (4), b= 14.649 (8), c= 13"964 (8)A, fl= 95"45 (8) ° and Z= 4, The structure was solved by the direct method and refined by least-squares calculations, using Ni-filtered Cu Ke diffractometer data. The final R index was 0.033 for 2232 reflections, and the standard deviations in the atomic positions are about 0.003 A. The two independent molecules have very similar conformations; the conformation about the glycosidic bond is anti, the sugar ring is puckered with C(Y) endo, and the conformation about C(4")-C(5') is gauchegauche.

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