We have cloned and sequenced the GAL2 gene of Saccharomyces cerevisiae, which encodes galactose permease. The GAL2 protein is related to the yeast glucose transporter encoded by the SNF3 gene, and also to mammalian and bacterial sugar permeases. Like the other members of this protein family, GAL2 has twelve hydrophobic segments that are separated by loops of charged amino acids. A comparison of different members of this protein family shows that those parts of the polypeptides thought to be on the cytoplasmic side of the cell membrane, are more conserved than other parts of the molecules.