The gene encoding the predominant facilitative glucose transporter expressed in pancreatic β-cells and hepatocytes, termed GLUT2, has been cloned and characterized. The human GLUT2 gene is composed of 11 exons spanning ∼30 kilobases. The sequence of the promoter region and all exons and adjacent intron regions has been determined and deposited in the GenBank database. Two highly polymorphic simple tandem repeat DNA polymorphisms useful for linkage studies were localized in introns 1 and 4a. In addition, a 168-base pair insertion/deletion polymorphism was identified in intron 3. The characterization of the human GLUT2 gene will facilitate studies of its role in the development of diabetes mellitus.