Glycosphingolipids (GSLs) are ubiquitous plasma membrane components composed of a ceramide lipid anchor attached to one of a diverse complement of oligosaccharide structures. Fundamentally important activities have been attributed to GSLs including formation of plasma membrane structures involved in membrane trafficking, signal transduction and cell-cell interactions. Glucosylceramide synthase converts ceramide to glucosylceramide, a core structure of the vast majority of GSLs. Disruption of the gene encoding glucosylceramide synthase (Ugcg) caused embryonic lethality in mice during gastrulation. To further investigate the role of GSL synthesis during embryogenesis, we produced mice with a Lacz reporter gene inserted into the glucosylceramide synthase locus. These mice allowed the visualization of glucosylceramide synthase expression during early embryonic development.