The synthesis of various galactose containing disaccharide nucleosides has been achieved by utilizing the transgalactosylation potential of beta-galactosidase from Aspergillus oryzae. Thus, using p-nitrophenyl-beta-D-galactoside 1 as galactosyl donor, 2-deoxyuridine 2a, uridine 2b, thymidine 2c and adenosine 2d have proven to be useful accepters for the enzyme catalyzed disaccharide nucleoside formation. The regiochemistry of the products 4a - 4d formed after acetylation has been assigned unambiguously by using modem NMR-techniques.