According to a classical tenet, sugar transport across animal membranes is restricted to monosaccharides. Here we report on the first animal disaccharide transporter, SCRT (SuCRose Transporter), which we detected in Drosophila melanogaster at each developmental stage. We localized the protein in apical membranes of the late embryonic hindgut as well as in vesicular membranes of ovarian follicle cells. The fact that knock-down of SCRT expression results in significantly increased lethality demonstrates an essential function for the protein. Experiments with Saccharomyces cerevisiae as a heterologous expression system revealed that sucrose is a transported substrate. Since the knock out of SLC45A2, a highly similar protein belonging to the mammalian Solute Carrier Family 45 (SLC45) causes oculocutaneous albinism and since the vesicular structures in which SCRT is located appear to contain melanin, we propose that these organelles are melanosome-like structures and that the transporter is necessary for balancing the osmotic equilibrium during the polymerization process of melanin by the import of a compatible osmolyte. In the hindgut epithelial cells sucrose may also serve as a compatible osmolyte, but we cannot exclude that transport of the disaccharide also serves nutritional adequacy.