Crystals of the 35 kDa protein haloalkane dehalogenase from Xanthobacter autotrophicus GJ10 diffract to 1.15 A Ê resolution at cryogenic temperature using synchrotron radiation. Blocked anisotropic least-squares re®nement with SHELXL gave a ®nal conventional R factor of 10.51% for all re¯ections in the 15±1.15 A Ê resolution range. The estimated r.m.s. errors of the model are 0.026 and 0.038 A Ê for protein atoms and all atoms, respectively. The structure comprises all 310 amino acids, with 28 side chains and two peptide bonds in multiple conformations, two covalently linked Pb atoms, 601 water molecules, seven glycerol molecules, one sulfate ion and two chloride ions. Water molecules accounting for alternative solvent structure are modelled with a ®xed occupancy of 0.5. The structure is described in detail and compared with previously reported dehalogenase structures re®ned at 1.9±2.3 A Ê resolution. An analysis of the protein's geometry and stereochemistry reveals eight mean values of bond lengths and angles which deviate signi®cantly from the Engh & Huber parameters, a wide spread in the main-chain 3 torsion angle around its ideal value of 180 (6) and a role for CÐHÁ Á ÁO interactions in satisfying the hydrogen-bond acceptor capacity of main-chain carbonyl O atoms in the central -sheet.