The SLC37 family of four predicted proteins is an almost unexplored group of transmembrane sugar transporters. Of the four proteins/genes assigned to date to this family, only one is well known, the SLC37A4 gene (also known as the glucose-6-phosphate transporter 1, G6PT1) mutated in the glycogen storage disease non-1A type. Data on SLC3A1 gene expression are available for humans, while data on SLC37A2 are available for mice. The last SLC37 family member, SLC37A3, is only a putative gene/protein identified by in silico analyses. The four genes are not clustered in a single chromosome as regions and the identity of their predicted polypeptides is between 60 and 20%. Here we propose a new nomenclature for the SLC37 proteins (SPX: sugar- phosphate e xchangers) numbered according to the gene numbering.