Several lines of evidence suggest the existence of additional members of the mammalian facilitative glucose transporter family. A human cDNA sequence corresponding to a novel member of the glucose transporter family (GLUT1–5) was identified (GLUT9; HGMW-approved symbol SLC2A9), and it encodes a putative transporter of 540 amino acids. The predicted protein has sequence identity of 44 and 38% to Glut5 and Glut1, respectively. Based on hydropathic analysis, the novel transporter's predicted topology consists of 12 transmembrane domains, similar to the other family members. Northern analysis reveals three mRNA species: a major transcript of 1.9 kb and two other transcripts of 3.1 and 5.0 kb, found primarily in kidney and liver, but present at low levels in several other tissues. GLUT9 was localized to chromosome 4 using a monochromosomal human/rodent somatic cell hybrid mapping panel. A portion of the GLUT9 cDNA is represented in a National Center for Biotechnology Information UniGene cluster, which maps to chromosome 4p15.3–p16.