It has been shown that all selectins recognize the carbohydrate epitopes sialyl Lewisx and sialyl Lewisa. For the establishment of the structure-activity relationship, the efficient synthesis of these tetrasaccharides and derivatives is therefore of vital interest. The glycosyl transferase-mediated approach is summarized with emphasis on the use of modified acceptors and modified sugar-nucleotide donors. A survey of the involved enzymes:13(1, 2, 3) and 13(1, 2, 3, 4)galactosyl transferases, a(2, 3)sialyl transferase, FucT Ill and FucT VI reveals that the enzymatic synthesis is highly efficient for the rapid preparation of sialyl Lewisx-and sialyl Lewisa-derivatives.