Unsaturated glucuronyl hydrolase from Bacillus sp. GL1 catalyzes the hydrolytic release of unsaturated glucuronic acids from oligosaccharides produced by the reactions of polysaccharide lyases such as gellan, xanthan, hyaluronate and chondroitin lyases. The enzyme was crystallized at 293 K from a droplet containing 56% MPD, 0.1 M NaCl, 0.1 M glycine-NaOH pH 8.2 and 0.1 M dithiothreitol using the vapour-diffusion method. The crystals were hexagonal and belonged to space group P6(1)22 or P6(5)22, with unit-cell parameters a = b = 102.8, c = 223.4 A. Diffraction data to 2.4 A were collected from a single crystal.