Repeated use of the in-situ modified reduced nickel catalyst prepared from nickel oxide was carried out for the enantio-differentiating hydrogenation of 2-octanone. The tartaric acid (TA)-NaBr in-situ modified reduced Ni retained over 60% of the enantio-differentiating ability (eda) of the catalyst in the hydrogenation at 373 K for repeated 16 runs by the addition of tartaric acid and sodium 2-ethylhexanoate to the reaction media before every other run. The quantitative analyses of the adsorbed species on the catalyst surface revealed that the tartaric acid and sodium ions adsorbed in the 1st run were gradually desorbed during the repeated runs. The result supports the necessity of the addition of tartaric acid and sodium 2-ethylhexanoate to the reaction media every other run for retaining the enantio-differentiating ability. (C) 2004 Elsevier B.V. All rights reserved.