N-Carbamoyl-L-amino-acid amidohydrolases (L-N-carbamoylases; EC 126.96.36.199) hydrolyze the carbon-nitrogen bond of the ureido group in N-carbamoyl-L-alpha-amino acids. These enzymes are commonly used in the production of optically pure natural and non-natural L-amino acids using the ;hydantoinase process'. Recombinant L-N-carbamoylase from Geobacillus stearothermophilus CECT43 has been expressed, purified and crystallized by hanging-drop vapour diffusion. X-ray data were collected to a resolution of 2.75 A. The crystals belonged to space group P2(1)2(1)2, with unit-cell parameters a = 103.2, b = 211.7, c = 43.1 A and two subunits in the asymmetric unit.