According to the classic point of view, transport of sugars across animal plasma membranes is performed by two families of transporters. Secondary active transport occurs via Na⁺ symporters of the SLC5 family, while passive transport occurs via facilitative transporters of the SLC2 family. Recently a new family appeared in the scenery which was called the SLC45 family of putative sugar transporters because one of its members had been shown to transport sugars, and because all members exhibit an apparent amino acid sequence identity to plant sucrose transporters of slightly above 20%. Although the human SLC45 family members (A1-A4) show only 20–30% identity among each other, based on derived amino acid sequences, they all feature twelve transmembrane domains with a large intracellular loop between transmembrane domains VI and VII, and have a signature sequence R-X-G-R-[K/R] between transmembrane domains II and III which is typical for plant sucrose transporters. Here we try to provide novel insights into the molecular features of SLC45 family members with a focus on their possible role as sugar transporters.