A high-resolution structure of the complex of Vibrio cholerae uridine phosphorylase (VchUPh) with its physiological ligand thymidine is important in order to determine the mechanism of the substrate specificity of the enzyme and for the rational design of pharmacological modulators. Here, the expression and purification of VchUPh and the crystallization of its complex with thymidine are reported. Conditions for crystallization were determined with an automated Cartesian Dispensing System using The Classics, MbClass and MbClass II Suites crystallization kits. Crystals of the VchUPh-thymidine complex (of dimensions similar to 200-350 mu m) were grown by the sitting-drop vapour-diffusion method in similar to 7 d at 291 K. The crystallization solution consisted of 1.5 mu l VchUPh (15 mg ml(-1)), 1 mu l 0.1 M thymidine and 1.5 mu l reservoir solution {[}15\%(w/v) PEG 4000, 0.2 M MgCl2 center dot 6H(2)O in 0.1 M Tris-HCl pH 8.5]. The crystals diffracted to 2.12 angstrom resolution and belonged to space group P2(1) (No. 4), with unit-cell parameters a = 91.80, b = 95.91, c = 91.89 angstrom, beta = 119.96 degrees. The Matthews coefficient was calculated as 2.18 angstrom(3) Da(-1); the corresponding solvent content was 43.74\%.