β-1,4-galactosyltransferase (GalTase) can be divided into short and long forms by its mRNA. The short form GalTase within the trans-Golgi compartment participates in the biosynthesis of glycoconjugates. The long form on cell surface mediates cell-cell and cell-matrix interactions by binding to appropriate glycoside substrates on adjacent cell surfaces or in the extracellular matrix, including spermatogenesis, sperm-egg binding, early embryo cell adhesion, secondary trophoblast giant cell migration and neurite outgrowth, and functions as a signal-transducing receptor for extracellular oligosaccharide ligands to affect G protein signal cascades. Surface GalTase also delivers a growth inhibitory signal by modulating the ability of the EGF receptor to transduce EGF-dependent signals, and plays an important role during cell growth.