The in situ modification of a reduced Ni catalyst at the first run showed a high durability for the repeated use with high optical yields in the enantio-differentiating hydrogenation of methyl acetoacetate. Reduced Ni from Ni oxide and fine Ni powder were the best materials in comparison with Raney Ni. For attaining high optical yields and high durability, in situ modification and a Ni surface suitable for the enantio-differentiating hydrogenation are necessary. One of the reasons for the low durability of the conventional pre-modified Ni with repeated use would be the desorption of tartaric acid from the catalyst surface during the hydrogenation reaction. (C) 2002 Elsevier Science B.V. All rights reserved.