UlaG, the putative L-ascorbate-6-phosphate lactonase encoded by the ulaG gene from the utilization of L-ascorbate regulon in Escherichia coli, has been cloned, overexpressed, purified using standard chromatographic techniques and crystallized. Crystals were obtained by sitting-drop vapour diffusion at 293 K. Preliminary X-ray diffraction analysis revealed that the UlaG crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 104.52, b = 180.69, c = 112.88 A, beta = 103.26 degrees. The asymmetric unit is expected to contain six copies of UlaG, with a corresponding volume per protein weight of 2.16 A3 Da(-1) and a solvent content of 43%.