Soluble epoxide hydrolase (EH) from the potato Solanum tuberosum and an evolved EH of the bacterium Agrobacterium radiobacter AD1, EchA-I219F, were purified for the enantioconvergent hydrolysis of racemic styrene oxide into the single product (R)-1-phenyl-1,2-ethanediol, which is an important intermediate for pharmaceuticals. EchA-I219F has enhanced enantioselectivity (enantiomeric ratio of 91 based on products) for converting (R)-styrene oxide to (R)-1-phenyl-1,2-ethanediol (2.0 ± 0.2 µmol/min/mg), and the potato EH converts (S)-styrene oxide primarily to the same enantiomer, (R)-1-phenyl-1,2-ethanediol (22 ± 1 µmol/min/mg), with an enantiomeric ratio of 40 ± 17 (based on substrates). By mixing these two purified enzymes, inexpensive racemic styrene oxide (5 mM) was converted at 100% yield to 98% enantiomeric excess (R)-1-phenyl-1,2-ethanediol at 4.7 ± 0.7 µmol/min/mg. Hence, at least 99% of substrate is converted into a single stereospecific product at a rapid rate. © 2006 Wiley Periodicals, Inc.