The Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase I86A mutant is stereospecific for (R)-alcohols instead of (S)-alcohols. Pyramidal crystals grown in the presence of (R)-phenylethanol via the hanging-drop vapour-diffusion method diffracted to 3.2 A resolution at the Canadian Light Source. The crystal belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 80.23, b = 124.90, c = 164.80 A. The structure was solved by molecular replacement using the structure of T. brockii SADH (PDB entry 1ykf).