Aspartate 1-decarboxylase (PanD) catalyzes the alpha-decarboxylation of L-aspartate in the major route of beta-alanine production for pantothenate biosynthesis in bacteria. Pantothenate is synthesized in microorganisms, plants and fungi but not in animals and thus the enzymes of its biosynthetic pathway are potential targets for developing agents against these organisms. PanD from the pathogenic bacterium Helicobacter pylori has been overexpressed in Escherichia coli and crystallized using sodium formate as a precipitant. Crystals diffracted to better than 1.5 A Bragg spacing upon exposure to synchrotron X-rays. Diffraction data to 1.55 A have been collected from a crystal grown in the presence of the substrate analogue isoasparagine. The crystal belongs to the tetragonal space group I422, with unit-cell parameters a = b = 81.83, c = 93.78 A. The asymmetric unit contains one subunit of PanD, with a corresponding crystal volume per protein mass (V(M)) of 2.85 A(3) Da(-1) and a solvent content of 56.8%.