The R-specific alcohol dehydrogenase (RADH) from Lactobacillus brevis is a valuable catalyst for the production of chiral alcohols that can be used as synthons in asymmetric syntheses. RADH is a homotetramer with 222 symmetry and a molecular mass of 107 kDa. The recombinant enzyme has been expressed in Escherichia coli, purified to homogeneity and crystallized. The crystals belong to the orthorhombic space group I222, with unit-cell parameters a = 56.5, b = 85.1, c = 115.4 A, and diffract X-rays to at least 1.8 A resolution. The calculated crystal packing parameter V(M) = 2.59 A(3) Da(-1), corresponding to a solvent content of 52.5% and suggesting that one RADH monomer is contained in the asymmetric unit. The RADH tetramer lies on a special position with its molecular dyads coinciding with the crystallographic twofold axes and with its centre of mass on the origin of the unit cell.