Roles of galactose and galactose metabolism in normal development, homeostasis, and disease. Galactose and its derivatives serve as essential components of glycoproteins and glycolipids in humans and other species. As a component of milk, galactose also serves as a key energy source for mammals, especially infants. Impaired metabolism of galactose leads to the potentially lethal disease classic galactosemia. We are applying a combination of basic and clinical approaches using patients, mammalian cells, flies, and microbial systems to explore the underlying bases of pathophysiology in galactosemia, and to define the roles of galactose and galactose metabolism in normal development and homeostasis. We are further working to develop novel and improved forms of intervention for patients with galactosemia.