A full-length cDNA clone for mouse N-acetylglucosamine (β 12-4)galactosyltransferase (β1-4GT) [EC 18.104.22.168] and several clones diverged from the β12-4GT cDNA were isolated from a mouse F9 cDNA library and then sequenced. The fβ1-4GT cDNA has an open reading frame consisting of 399 amino acids. The homology at the amino acid level is 80 and 91% as to the partial sequences of bovine and human milk β12-4GT respectively. The general enzyme structure of the β1-4GT seems to be similar to that of a rat β-galactoside (α2-6) sialyltransferase. Junctions of the common and divergent regions of cDNA have dinucleotides, AG, suggesting that the variety of cDNA clones is generated through alternative splicing. © 1988 BY The Journal of Biochemistry.